fanotify: introduce new event types FAN_OPEN_EXEC and FAN_OPEN_EXEC_PERM

PATCH Superseded Matthew Bobrowski 3 participants 13 messages Oct 11, 2018 – Oct 17, 2018

Subsystems (3)

VFS Fsnotify: filesystem notification infrastructure Fanotify

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Matthew Bobrowski

author

2018-10-11 18:08 UTC #0 lore raw

v4 cover fanotify: introduce new event types FAN_OPEN_EXEC and FAN_OPEN_EXEC_PERM

Currently, the fanotify API does not provide a means for user space applications to receive events when a file has been opened specifically for execution. New event types FAN_OPEN_EXEC and FAN_OPEN_EXEC_PERM have been introduced in order to provide users this capability.

These event types, when either are explicitly requested by the user, will be returned within the event mask when a marked file object is being opened has __FMODE_EXEC set as one of the flags for open_flag.

Linux is used as an operating system in some products, with an environment that can be certified under the Common Criteria Operating System Protection Profile (OSPP). This is a formal threat model for a class of technology. It requires specific countermeasures to mitigate threats. It requires documentation to explain how a product implements these countermeasures. It requires proof via a test suite to demonstrate that the requirements are met, observed and checked by an independent qualified third party. The latest set of requirements for OSPP v4.2 can be found here:

https://www.niap-ccevs.org/Profile/Info.cfm?PPID=424&id=424

If you look on page 58, you will see the following requirement:

FPT_SRP_EXT.1 Software Restriction Policies FPT_SRP_EXT.1.1 administrator specified [selection:
file path,
file digital signature,
version,
hash,
[assignment: other characteristics]
]

This patch is to help aid in meeting this requirement.

I've also written the required updates for the man-pages project. You can find the necessary changes for these new event types within the following commit:

https://github.com/matthewbobrowski/man-pages/commit/d075dd8c8dfe19fccb9ea91f9550ea41b6e67334

Please note that all modifications here are based on the changes Amir has made around deprecating some of the previously exposed UAPI constants. The branch which my changes are based on can be found here:

https://github.com/amir73il/linux/tree/fanotify_api-v3

Lastly, thanks to both Amir and Jan for their help and feedback along the way, truly appreciated.

---

Matthew Bobrowski (3):
fanotify: introduce new event type FAN_OPEN_EXEC
fanotify: return only user requested event types in event mask
fanotify: introduce new event type FAN_OPEN_EXEC_PERM

 fs/notify/fanotify/fanotify.c    | 50 ++++++++++++++++++--------------
 fs/notify/fsnotify.c             |  2 +-
 include/linux/fanotify.h         |  5 ++--
 include/linux/fsnotify.h         | 12 +++++---
 include/linux/fsnotify_backend.h | 10 +++++--
 include/uapi/linux/fanotify.h    |  2 ++
 6 files changed, 50 insertions(+), 31 deletions(-)

Signature · 1 line

2.17.2

Matthew Bobrowski

author

2018-10-11 18:09 UTC #1 lore raw

PATCH v4 1/3 fanotify: introduce new event type FAN_OPEN_EXEC

A new event type FAN_OPEN_EXEC has been defined so that users have the ability to receive events specifically when a file has been opened with the intent to be executed.

The FAN_OPEN_EXEC flag is set within the fsnotify_open() hook only if a file has the __FMODE_EXEC bit set within file->f_flags.

Signed-off-by Matthew Bobrowski <[email protected]>

---
 fs/notify/fanotify/fanotify.c    | 3 ++-
 fs/notify/fsnotify.c             | 2 +-
 include/linux/fanotify.h         | 2 +-
 include/linux/fsnotify.h         | 2 ++
 include/linux/fsnotify_backend.h | 7 +++++--
 include/uapi/linux/fanotify.h    | 1 +
 6 files changed, 12 insertions(+), 5 deletions(-)

fs/notify/fanotify/fanotify.c +2 -1

index 2c57186caa2e..b3e92302ed84 100644
@@ -207,8 +207,9 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
+	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 10);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
 
 	if (!fanotify_should_send_event(iter_info, mask, data, data_type))
 		return 0;

fs/notify/fsnotify.c +1 -1

index a0ad06285450..051e5fc0dba1 100644
@@ -402,7 +402,7 @@ static __init int fsnotify_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 24);
 
 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)

include/linux/fanotify.h +1 -1

index 05b696b4856b..0e07d23b6c17 100644
@@ -39,7 +39,7 @@
 
 /* Events that user can request to be notified on */
 #define FANOTIFY_EVENTS		(FAN_ACCESS | FAN_MODIFY | \
-				 FAN_CLOSE | FAN_OPEN)
+				 FAN_CLOSE | FAN_OPEN | FAN_OPEN_EXEC)
 
 /* Events that require a permission response from user */
 #define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM)

include/linux/fsnotify.h +2 -0

index fd1ce10553bf..1fe5ac93b252 100644
@@ -215,6 +215,8 @@ static inline void fsnotify_open(struct file *file)
 
 	if (S_ISDIR(inode->i_mode))
 		mask |= FS_ISDIR;
+	if (file->f_flags & __FMODE_EXEC)
+		mask |= FS_OPEN_EXEC;
 
 	fsnotify_parent(path, NULL, mask);
 	fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);

include/linux/fsnotify_backend.h +5 -2

index 135b973e44d1..329ac6684326 100644
@@ -38,6 +38,7 @@
 #define FS_DELETE		0x00000200	/* Subfile was deleted */
 #define FS_DELETE_SELF		0x00000400	/* Self was deleted */
 #define FS_MOVE_SELF		0x00000800	/* Self was moved */
+#define FS_OPEN_EXEC		0x00001000	/* File was opened for exec */
 
 #define FS_UNMOUNT		0x00002000	/* inode on umount fs */
 #define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */

@@ -62,7 +63,8 @@
 #define FS_EVENTS_POSS_ON_CHILD   (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
 				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
 				   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
-				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM)
+				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM |\
+				   FS_OPEN_EXEC)
 
 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)

@@ -74,7 +76,8 @@
 			     FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
 			     FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
-			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME)
+			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME |\
+			     FS_OPEN_EXEC)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \

include/uapi/linux/fanotify.h +1 -0

index 00b2304ed124..da278f11ab29 100644
@@ -10,6 +10,7 @@
 #define FAN_CLOSE_WRITE		0x00000008	/* Writtable file closed */
 #define FAN_CLOSE_NOWRITE	0x00000010	/* Unwrittable file closed */
 #define FAN_OPEN		0x00000020	/* File was opened */
+#define FAN_OPEN_EXEC		0x00001000	/* File was opened for exec */
 
 #define FAN_Q_OVERFLOW		0x00004000	/* Event queued overflowed */

Signature · 1 line

2.17.2

Jan Kara

maintainer

2018-10-16 19:48 UTC #2 lore raw

Re: [PATCH v4 1/3] fanotify: introduce new event type FAN_OPEN_EXEC

Quoted 3 lines · Matthew Bobrowski

A new event type FAN_OPEN_EXEC has been defined so that users have the ability to receive events specifically when a file has been opened with the intent to be executed.

Can we perhaps expand this a bit to clarify that this means execve(), execve_at(), and uselib() syscalls? Then the sentence below could just clarify that feature is implemented by fanotify_open() generating FAN_OPEN_EXEC event if __FMODE_EXEC is set within file->f_flags. Thanks!

Honza

Quoted 114 lines

The FAN_OPEN_EXEC flag is set within the fsnotify_open() hook only if a file has the __FMODE_EXEC bit set within file->f_flags.

Signed-off-by Matthew Bobrowski <[email protected]>

---
 fs/notify/fanotify/fanotify.c    | 3 ++-
 fs/notify/fsnotify.c             | 2 +-
 include/linux/fanotify.h         | 2 +-
 include/linux/fsnotify.h         | 2 ++
 include/linux/fsnotify_backend.h | 7 +++++--
 include/uapi/linux/fanotify.h    | 1 +
 6 files changed, 12 insertions(+), 5 deletions(-)

fs/notify/fanotify/fanotify.c +2 -1

index 2c57186caa2e..b3e92302ed84 100644
@@ -207,8 +207,9 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
+	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 10);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
 
 	if (!fanotify_should_send_event(iter_info, mask, data, data_type))
 		return 0;

fs/notify/fsnotify.c +1 -1

index a0ad06285450..051e5fc0dba1 100644
@@ -402,7 +402,7 @@ static __init int fsnotify_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 24);
 
 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)

include/linux/fanotify.h +1 -1

index 05b696b4856b..0e07d23b6c17 100644
@@ -39,7 +39,7 @@
 
 /* Events that user can request to be notified on */
 #define FANOTIFY_EVENTS		(FAN_ACCESS | FAN_MODIFY | \
-				 FAN_CLOSE | FAN_OPEN)
+				 FAN_CLOSE | FAN_OPEN | FAN_OPEN_EXEC)
 
 /* Events that require a permission response from user */
 #define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM)

include/linux/fsnotify.h +2 -0

index fd1ce10553bf..1fe5ac93b252 100644
@@ -215,6 +215,8 @@ static inline void fsnotify_open(struct file *file)
 
 	if (S_ISDIR(inode->i_mode))
 		mask |= FS_ISDIR;
+	if (file->f_flags & __FMODE_EXEC)
+		mask |= FS_OPEN_EXEC;
 
 	fsnotify_parent(path, NULL, mask);
 	fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);

include/linux/fsnotify_backend.h +5 -2

index 135b973e44d1..329ac6684326 100644
@@ -38,6 +38,7 @@
 #define FS_DELETE		0x00000200	/* Subfile was deleted */
 #define FS_DELETE_SELF		0x00000400	/* Self was deleted */
 #define FS_MOVE_SELF		0x00000800	/* Self was moved */
+#define FS_OPEN_EXEC		0x00001000	/* File was opened for exec */
 
 #define FS_UNMOUNT		0x00002000	/* inode on umount fs */
 #define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */

@@ -62,7 +63,8 @@
 #define FS_EVENTS_POSS_ON_CHILD   (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
 				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
 				   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
-				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM)
+				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM |\
+				   FS_OPEN_EXEC)
 
 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)

@@ -74,7 +76,8 @@
 			     FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
 			     FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
-			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME)
+			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME |\
+			     FS_OPEN_EXEC)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \

include/uapi/linux/fanotify.h +1 -0

index 00b2304ed124..da278f11ab29 100644
@@ -10,6 +10,7 @@
 #define FAN_CLOSE_WRITE		0x00000008	/* Writtable file closed */
 #define FAN_CLOSE_NOWRITE	0x00000010	/* Unwrittable file closed */
 #define FAN_OPEN		0x00000020	/* File was opened */
+#define FAN_OPEN_EXEC		0x00001000	/* File was opened for exec */
 
 #define FAN_Q_OVERFLOW		0x00004000	/* Event queued overflowed */

Signature · 1 line

2.17.2

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Matthew Bobrowski

author

2018-10-17 14:24 UTC #3 lore raw

Re: [PATCH v4 1/3] fanotify: introduce new event type FAN_OPEN_EXEC

Quoted 9 lines · Jan Kara

Quoted 3 lines · Matthew Bobrowski
A new event type FAN_OPEN_EXEC has been defined so that users have the ability to receive events specifically when a file has been opened with the intent to be executed.
Can we perhaps expand this a bit to clarify that this means execve(), execve_at(), and uselib() syscalls? Then the sentence below could just clarify that feature is implemented by fanotify_open() generating FAN_OPEN_EXEC event if __FMODE_EXEC is set within file->f_flags. Thanks!

Updated.

I will include these updates within the new patch series I'm going to post through.

Quoted 117 lines

Quoted 114 lines

The FAN_OPEN_EXEC flag is set within the fsnotify_open() hook only if a file has the __FMODE_EXEC bit set within file->f_flags.

Signed-off-by Matthew Bobrowski <[email protected]>

---
 fs/notify/fanotify/fanotify.c    | 3 ++-
 fs/notify/fsnotify.c             | 2 +-
 include/linux/fanotify.h         | 2 +-
 include/linux/fsnotify.h         | 2 ++
 include/linux/fsnotify_backend.h | 7 +++++--
 include/uapi/linux/fanotify.h    | 1 +
 6 files changed, 12 insertions(+), 5 deletions(-)

fs/notify/fanotify/fanotify.c +2 -1

index 2c57186caa2e..b3e92302ed84 100644
@@ -207,8 +207,9 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
+	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 10);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
 
 	if (!fanotify_should_send_event(iter_info, mask, data, data_type))
 		return 0;

fs/notify/fsnotify.c +1 -1

index a0ad06285450..051e5fc0dba1 100644
@@ -402,7 +402,7 @@ static __init int fsnotify_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 24);
 
 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)

include/linux/fanotify.h +1 -1

index 05b696b4856b..0e07d23b6c17 100644
@@ -39,7 +39,7 @@
 
 /* Events that user can request to be notified on */
 #define FANOTIFY_EVENTS		(FAN_ACCESS | FAN_MODIFY | \
-				 FAN_CLOSE | FAN_OPEN)
+				 FAN_CLOSE | FAN_OPEN | FAN_OPEN_EXEC)
 
 /* Events that require a permission response from user */
 #define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM)

include/linux/fsnotify.h +2 -0

index fd1ce10553bf..1fe5ac93b252 100644
@@ -215,6 +215,8 @@ static inline void fsnotify_open(struct file *file)
 
 	if (S_ISDIR(inode->i_mode))
 		mask |= FS_ISDIR;
+	if (file->f_flags & __FMODE_EXEC)
+		mask |= FS_OPEN_EXEC;
 
 	fsnotify_parent(path, NULL, mask);
 	fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);

include/linux/fsnotify_backend.h +5 -2

index 135b973e44d1..329ac6684326 100644
@@ -38,6 +38,7 @@
 #define FS_DELETE		0x00000200	/* Subfile was deleted */
 #define FS_DELETE_SELF		0x00000400	/* Self was deleted */
 #define FS_MOVE_SELF		0x00000800	/* Self was moved */
+#define FS_OPEN_EXEC		0x00001000	/* File was opened for exec */
 
 #define FS_UNMOUNT		0x00002000	/* inode on umount fs */
 #define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */

@@ -62,7 +63,8 @@
 #define FS_EVENTS_POSS_ON_CHILD   (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\
 				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
 				   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
-				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM)
+				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM |\
+				   FS_OPEN_EXEC)
 
 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)

@@ -74,7 +76,8 @@
 			     FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \
 			     FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
-			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME)
+			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME |\
+			     FS_OPEN_EXEC)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \

include/uapi/linux/fanotify.h +1 -0

index 00b2304ed124..da278f11ab29 100644
@@ -10,6 +10,7 @@
 #define FAN_CLOSE_WRITE		0x00000008	/* Writtable file closed */
 #define FAN_CLOSE_NOWRITE	0x00000010	/* Unwrittable file closed */
 #define FAN_OPEN		0x00000020	/* File was opened */
+#define FAN_OPEN_EXEC		0x00001000	/* File was opened for exec */
 
 #define FAN_Q_OVERFLOW		0x00004000	/* Event queued overflowed */

Signature · 1 line

2.17.2

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Matthew Bobrowski

author

2018-10-11 18:09 UTC #4 lore raw

PATCH v4 2/3 fanotify: return only user requested event types in event mask

In reply to Matthew Bobrowski

Modified fanotify_should_send_event() so that it now returns a mask for a event that contains ONLY flags for the event types that have been specifically requested by the user. Flags that may have been included within the event mask, but have not been explicitly requested by the user will not be present in the returned value.

As an example, given the situation where a user requests events of type FAN_OPEN. Traditionally, the event mask returned within an event that occurred on a filesystem object that has been marked for monitoring and is opened, will only ever have the FAN_OPEN bit set. With the introduction of the new flags like FAN_OPEN_EXEC, and perhaps any other future event flags, there is a possibility of the returned event mask containing more than a single bit set, despite having only requested the single event type. Prior to these modifications performed to fanotify_should_send_event(), a user would have received a bundled event mask containing flags FAN_OPEN and FAN_OPEN_EXEC in the instance that a file was opened for execution via execve(), for example. This means that a user would receive event types in the returned event mask that have not been requested. This runs the possibility of breaking existing systems and causing other unforeseen issues.

To mitigate this possibility, fanotify_should_send_event() has been modified to return the event mask containing ONLY event types explicitly requested by the user. This means that we will NOT report events that the user did no set a mask for, and we will NOT report events that the user has set an ignore mask for.

The function name fanotify_should_send_event() has also been updated so that it's more relevant to what it has been designed to do.

Signed-off-by Matthew Bobrowski <[email protected]>

---
 fs/notify/fanotify/fanotify.c | 46 ++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 20 deletions(-)

fs/notify/fanotify/fanotify.c +26 ~~-20~~

index b3e92302ed84..9da334d343b8 100644
@@ -89,7 +89,13 @@ static int fanotify_get_response(struct fsnotify_group *group,
 	return ret;
 }
 
-static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
+/*
+ * This function returns a mask for a event that only contains the flags
+ * that have been specifically requested by the user. Flags that may have
+ * been included within the event mask, but have not been ecplicitly
+ * requested by the user, will not be present in the returned mask.
+ */
+static u32 fanotify_group_event_mask(struct fsnotify_iter_info *iter_info,
 				       u32 event_mask, const void *data,
 				       int data_type)
 {

@@ -101,21 +107,21 @@ static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
 	pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
 		 __func__, iter_info->report_mask, event_mask, data, data_type);
 
-	/* if we don't have enough info to send an event to userspace say no */
+	/* If we don't have enough info to send an event to userspace say no */
 	if (data_type != FSNOTIFY_EVENT_PATH)
-		return false;
+		return 0;
 
-	/* sorry, fanotify only gives a damn about files and dirs */
+	/* Sorry, fanotify only gives a damn about files and dirs */
 	if (!d_is_reg(path->dentry) &&
 	    !d_can_lookup(path->dentry))
-		return false;
+		return 0;
 
 	fsnotify_foreach_obj_type(type) {
 		if (!fsnotify_iter_should_report_type(iter_info, type))
 			continue;
 		mark = iter_info->marks[type];
 		/*
-		 * if the event is for a child and this inode doesn't care about
+		 * If the event is for a child and this inode doesn't care about
 		 * events on the child, don't send it!
 		 */
 		if (type == FSNOTIFY_OBJ_TYPE_INODE &&

@@ -129,13 +135,10 @@ static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
 
 	if (d_is_dir(path->dentry) &&
 	    !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
-		return false;
-
-	if (event_mask & FANOTIFY_OUTGOING_EVENTS &
-	    marks_mask & ~marks_ignored_mask)
-		return true;
+		return 0;
 
-	return false;
+	return event_mask & FANOTIFY_OUTGOING_EVENTS & marks_mask &
+		~marks_ignored_mask;
 }
 
 struct fanotify_event_info *fanotify_alloc_event(struct fsnotify_group *group,

@@ -194,6 +197,7 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 				 struct fsnotify_iter_info *iter_info)
 {
 	int ret = 0;
+	u32 event_mask = 0;
 	struct fanotify_event_info *event;
 	struct fsnotify_event *fsn_event;

@@ -211,13 +215,15 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 
 	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
 
-	if (!fanotify_should_send_event(iter_info, mask, data, data_type))
+	event_mask = fanotify_group_event_mask(iter_info, mask, data,
+						data_type);
+	if (!event_mask)
 		return 0;
 
 	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
-		 mask);
+		 event_mask);
 
-	if (fanotify_is_perm_event(mask)) {
+	if (fanotify_is_perm_event(event_mask)) {
 		/*
 		 * fsnotify_prepare_user_wait() fails if we race with mark
 		 * deletion.  Just let the operation pass in that case.

@@ -226,14 +232,14 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 			return 0;
 	}
 
-	event = fanotify_alloc_event(group, inode, mask, data);
+	event = fanotify_alloc_event(group, inode, event_mask, data);
 	ret = -ENOMEM;
 	if (unlikely(!event)) {
 		/*
 		 * We don't queue overflow events for permission events as
 		 * there the access is denied and so no event is in fact lost.
 		 */
-		if (!fanotify_is_perm_event(mask))
+		if (!fanotify_is_perm_event(event_mask))
 			fsnotify_queue_overflow(group);
 		goto finish;
 	}

@@ -242,18 +248,18 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
 	if (ret) {
 		/* Permission events shouldn't be merged */
-		BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
+		BUG_ON(ret == 1 && event_mask & FANOTIFY_PERM_EVENTS);
 		/* Our event wasn't used in the end. Free it. */
 		fsnotify_destroy_event(group, fsn_event);
 
 		ret = 0;
-	} else if (fanotify_is_perm_event(mask)) {
+	} else if (fanotify_is_perm_event(event_mask)) {
 		ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event),
 					    iter_info);
 		fsnotify_destroy_event(group, fsn_event);
 	}
 finish:
-	if (fanotify_is_perm_event(mask))
+	if (fanotify_is_perm_event(event_mask))
 		fsnotify_finish_user_wait(iter_info);
 
 	return ret;

Signature · 1 line

2.17.2

Amir Goldstein

reviewer

2018-10-11 18:30 UTC #5 lore raw

Re: [PATCH v4 2/3] fanotify: return only user requested event types in event mask

Quoted 28 lines · Matthew Bobrowski

Modified fanotify_should_send_event() so that it now returns a mask for a event that contains ONLY flags for the event types that have been specifically requested by the user. Flags that may have been included within the event mask, but have not been explicitly requested by the user will not be present in the returned value.
As an example, given the situation where a user requests events of type FAN_OPEN. Traditionally, the event mask returned within an event that occurred on a filesystem object that has been marked for monitoring and is opened, will only ever have the FAN_OPEN bit set. With the introduction of the new flags like FAN_OPEN_EXEC, and perhaps any other future event flags, there is a possibility of the returned event mask containing more than a single bit set, despite having only requested the single event type. Prior to these modifications performed to fanotify_should_send_event(), a user would have received a bundled event mask containing flags FAN_OPEN and FAN_OPEN_EXEC in the instance that a file was opened for execution via execve(), for example. This means that a user would receive event types in the returned event mask that have not been requested. This runs the possibility of breaking existing systems and causing other unforeseen issues.
To mitigate this possibility, fanotify_should_send_event() has been modified to return the event mask containing ONLY event types explicitly requested by the user. This means that we will NOT report events that the user did no set a mask for, and we will NOT report events that the user has set an ignore mask for.

Quoted 5 lines

The function name fanotify_should_send_event() has also been updated so that it's more relevant to what it has been designed to do.
Signed-off-by Matthew Bobrowski <[email protected]>
---

I feel that this story could be shorter and less confusing, but I cannot offer a better version, nor do I object to this version. Maybe Jan can give it some final touches.

Thanks,
Amir.

Jan Kara

maintainer

2018-10-16 19:42 UTC #6 lore raw

Re: [PATCH v4 2/3] fanotify: return only user requested event types in event mask

In reply to Matthew Bobrowski

Hi,

the patch looks good. Just couple nits:

Quoted 1 line · Matthew Bobrowski

Modified fanotify_should_send_event() so that it now returns a mask for

^^ Modify

Quoted 1 line

a event that contains ONLY flags for the event types that have been

^ an

Quoted 38 lines

specifically requested by the user. Flags that may have been included within the event mask, but have not been explicitly requested by the user will not be present in the returned value.
As an example, given the situation where a user requests events of type FAN_OPEN. Traditionally, the event mask returned within an event that occurred on a filesystem object that has been marked for monitoring and is opened, will only ever have the FAN_OPEN bit set. With the introduction of the new flags like FAN_OPEN_EXEC, and perhaps any other future event flags, there is a possibility of the returned event mask containing more than a single bit set, despite having only requested the single event type. Prior to these modifications performed to fanotify_should_send_event(), a user would have received a bundled event mask containing flags FAN_OPEN and FAN_OPEN_EXEC in the instance that a file was opened for execution via execve(), for example. This means that a user would receive event types in the returned event mask that have not been requested. This runs the possibility of breaking existing systems and causing other unforeseen issues.
To mitigate this possibility, fanotify_should_send_event() has been modified to return the event mask containing ONLY event types explicitly requested by the user. This means that we will NOT report events that the user did no set a mask for, and we will NOT report events that the user has set an ignore mask for.
The function name fanotify_should_send_event() has also been updated so that it's more relevant to what it has been designed to do.
Signed-off-by Matthew Bobrowski <[email protected]>
---
 fs/notify/fanotify/fanotify.c | 46 ++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 20 deletions(-)
fs/notify/fanotify/fanotify.c +0 -0
index b3e92302ed84..9da334d343b8 100644

fs/notify/fanotify/fanotify.c static int fanotify_get_response(struct fsnotify_group *group, · line 93

Quoted 6 lines

fs/notify/fanotify/fanotify.c +2 -1

@@ -89,7 +89,13 @@ static int fanotify_get_response(struct fsnotify_group *group,
 	return ret;
 }
 
-static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
+/*
+ * This function returns a mask for a event that only contains the flags

				      ^^ an

fs/notify/fanotify/fanotify.c static int fanotify_get_response(struct fsnotify_group *group, · line 95

Quoted 2 lines

fs/notify/fanotify/fanotify.c +2 -0

+ * that have been specifically requested by the user. Flags that may have
+ * been included within the event mask, but have not been ecplicitly

^^ explicitly

Quoted 5 lines

fs/notify/fanotify/fanotify.c +3 -0

+ * requested by the user, will not be present in the returned mask.
+ */
+static u32 fanotify_group_event_mask(struct fsnotify_iter_info *iter_info,
 				       u32 event_mask, const void *data,
 				       int data_type)

<snip>

Quoted 10 lines

struct fanotify_event_info *fanotify_alloc_event(struct fsnotify_group *group,

fs/notify/fanotify/fanotify.c +1 -0

@@ -194,6 +197,7 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 				 struct fsnotify_iter_info *iter_info)
 {
 	int ret = 0;
+	u32 event_mask = 0;
 	struct fanotify_event_info *event;
 	struct fsnotify_event *fsn_event;

fs/notify/fanotify/fanotify.c static int fanotify_handle_event(struct fsnotify_group *group, · line 219

Quoted 6 lines

fs/notify/fanotify/fanotify.c +2 -1

@@ -211,13 +215,15 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 
 	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
 
-	if (!fanotify_should_send_event(iter_info, mask, data, data_type))
+	event_mask = fanotify_group_event_mask(iter_info, mask, data,
+						data_type);

^^^ Why don't you store the result in 'mask'? You don't need
the original mask later anyway, it reduces churn and also possibility of getting things wrong in the future...

Honza

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Matthew Bobrowski

author

2018-10-17 14:24 UTC #7 lore raw

Re: [PATCH v4 2/3] fanotify: return only user requested event types in event mask

Quoted 8 lines · Jan Kara

Hi,
the patch looks good. Just couple nits:
Quoted 1 line · Matthew Bobrowski
Modified fanotify_should_send_event() so that it now returns a mask for
^^ Modify

Updated.

Quoted 2 lines

Quoted 1 line
a event that contains ONLY flags for the event types that have been
^ an

Updated.

Quoted 41 lines

Quoted 41 lines
specifically requested by the user. Flags that may have been included within the event mask, but have not been explicitly requested by the user will not be present in the returned value.
As an example, given the situation where a user requests events of type FAN_OPEN. Traditionally, the event mask returned within an event that occurred on a filesystem object that has been marked for monitoring and is opened, will only ever have the FAN_OPEN bit set. With the introduction of the new flags like FAN_OPEN_EXEC, and perhaps any other future event flags, there is a possibility of the returned event mask containing more than a single bit set, despite having only requested the single event type. Prior to these modifications performed to fanotify_should_send_event(), a user would have received a bundled event mask containing flags FAN_OPEN and FAN_OPEN_EXEC in the instance that a file was opened for execution via execve(), for example. This means that a user would receive event types in the returned event mask that have not been requested. This runs the possibility of breaking existing systems and causing other unforeseen issues.
To mitigate this possibility, fanotify_should_send_event() has been modified to return the event mask containing ONLY event types explicitly requested by the user. This means that we will NOT report events that the user did no set a mask for, and we will NOT report events that the user has set an ignore mask for.
The function name fanotify_should_send_event() has also been updated so that it's more relevant to what it has been designed to do.
Signed-off-by Matthew Bobrowski <[email protected]>
---
 fs/notify/fanotify/fanotify.c | 46 ++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 20 deletions(-)
fs/notify/fanotify/fanotify.c +0 -0
index b3e92302ed84..9da334d343b8 100644
@@ -89,7 +89,13 @@ static int fanotify_get_response(struct fsnotify_group *group,
 	return ret;
 }
 

Quoted 4 lines

fs/notify/fanotify/fanotify.c static int fanotify_get_response(struct fsnotify_group *group, · line 93
Quoted 3 lines
fs/notify/fanotify/fanotify.c +2 -1
-static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
+/*
+ * This function returns a mask for a event that only contains the flags
				      ^^ an

Updated.

Quoted 3 lines

fs/notify/fanotify/fanotify.c static int fanotify_get_response(struct fsnotify_group *group, · line 95
Quoted 2 lines
fs/notify/fanotify/fanotify.c +2 -0
+ * that have been specifically requested by the user. Flags that may have
+ * been included within the event mask, but have not been ecplicitly
^^ explicitly

Updated.

Quoted 19 lines

Quoted 5 lines

fs/notify/fanotify/fanotify.c +3 -0

+ * requested by the user, will not be present in the returned mask.
+ */
+static u32 fanotify_group_event_mask(struct fsnotify_iter_info *iter_info,
 				       u32 event_mask, const void *data,
 				       int data_type)

<snip>

Quoted 11 lines

struct fanotify_event_info *fanotify_alloc_event(struct fsnotify_group *group,

fs/notify/fanotify/fanotify.c +1 -0

@@ -194,6 +197,7 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 				 struct fsnotify_iter_info *iter_info)
 {
 	int ret = 0;
+	u32 event_mask = 0;
 	struct fanotify_event_info *event;
 	struct fsnotify_event *fsn_event;

@@ -211,13 +215,15 @@ static int fanotify_handle_event(struct fsnotify_group *group,

Quoted 8 lines

fs/notify/fanotify/fanotify.c static int fanotify_handle_event(struct fsnotify_group *group, · line 219
Quoted 5 lines
fs/notify/fanotify/fanotify.c +2 -1
 	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
 
-	if (!fanotify_should_send_event(iter_info, mask, data, data_type))
+	event_mask = fanotify_group_event_mask(iter_info, mask, data,
+						data_type);
^^^ Why don't you store the result in 'mask'? You don't need
the original mask later anyway, it reduces churn and also possibility of getting things wrong in the future...

Good point. There's no real reason why we can't overwrite the original 'mask' value with the returned value from fanotify_group_event_mask(). That being said, I've gone ahead and applied updates accordingly.

I will post through the updates within an updated patch series.

Matthew Bobrowski

author

2018-10-11 18:09 UTC #8 lore raw

PATCH v4 3/3 fanotify: introduce new event type FAN_OPEN_EXEC_PERM

In reply to Matthew Bobrowski

A new event type FAN_OPEN_EXEC_PERM has been defined. This allows users to receive and grant access to files that are intending to be opened for execution.

This acts in the same manor as previous permission event types, meaning that a access response is required from the application to permit further operations on the file. The event flag is set specifically when the __FMODE_EXEC flag is set within file->f_flags in the fsnotify_perm() hook.

Signed-off-by Matthew Bobrowski <[email protected]>

---
 fs/notify/fanotify/fanotify.c    |  3 ++-
 fs/notify/fsnotify.c             |  2 +-
 include/linux/fanotify.h         |  3 ++-
 include/linux/fsnotify.h         | 10 ++++++----
 include/linux/fsnotify_backend.h |  7 ++++---
 include/uapi/linux/fanotify.h    |  1 +
 6 files changed, 16 insertions(+), 10 deletions(-)

fs/notify/fanotify/fanotify.c +2 -1

index 9da334d343b8..bae9a312d772 100644
@@ -212,8 +212,9 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
 	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
+	BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 12);
 
 	event_mask = fanotify_group_event_mask(iter_info, mask, data,
 						data_type);

fs/notify/fsnotify.c +1 -1

index 051e5fc0dba1..40ed97aede29 100644
@@ -402,7 +402,7 @@ static __init int fsnotify_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 24);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);
 
 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)

include/linux/fanotify.h +2 -1

index 0e07d23b6c17..614943153596 100644
@@ -42,7 +42,8 @@
 				 FAN_CLOSE | FAN_OPEN | FAN_OPEN_EXEC)
 
 /* Events that require a permission response from user */
-#define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM)
+#define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM | \
+				 FAN_OPEN_EXEC_PERM)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define FANOTIFY_EVENT_FLAGS	(FAN_EVENT_ON_CHILD | FAN_ONDIR)

include/linux/fsnotify.h +6 -4

index 1fe5ac93b252..6fb8d1fcfeaf 100644
@@ -38,12 +38,14 @@ static inline int fsnotify_perm(struct file *file, int mask)
 		return 0;
 	if (!(mask & (MAY_READ | MAY_OPEN)))
 		return 0;
-	if (mask & MAY_OPEN)
+	if (mask & MAY_OPEN) {
 		fsnotify_mask = FS_OPEN_PERM;
-	else if (mask & MAY_READ)
+
+		if (file->f_flags & __FMODE_EXEC)
+			fsnotify_mask |= FS_OPEN_EXEC_PERM;
+	} else if (mask & MAY_READ) {
 		fsnotify_mask = FS_ACCESS_PERM;
-	else
-		BUG();
+	}
 
 	ret = fsnotify_parent(path, NULL, fsnotify_mask);
 	if (ret)

include/linux/fsnotify_backend.h +4 -3

index 329ac6684326..96616651220c 100644
@@ -44,8 +44,9 @@
 #define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */
 #define FS_IN_IGNORED		0x00008000	/* last inotify event here */
 
-#define FS_OPEN_PERM		0x00010000	/* open event in an permission hook */
+#define FS_OPEN_PERM		0x00010000	/* open event in a permission hook */
 #define FS_ACCESS_PERM		0x00020000	/* access event in a permissions hook */
+#define FS_OPEN_EXEC_PERM	0x00040000	/* open/exec in a permission hook */
 
 #define FS_EXCL_UNLINK		0x04000000	/* do not send events if object is unlinked */
 #define FS_ISDIR		0x40000000	/* event occurred against dir */

@@ -64,7 +65,7 @@
 				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
 				   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
 				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM |\
-				   FS_OPEN_EXEC)
+				   FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
 
 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)

@@ -77,7 +78,7 @@
 			     FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
 			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME |\
-			     FS_OPEN_EXEC)
+			     FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \

include/uapi/linux/fanotify.h +1 -0

index da278f11ab29..e2df10c61cb1 100644
@@ -16,6 +16,7 @@
 
 #define FAN_OPEN_PERM		0x00010000	/* File open in perm check */
 #define FAN_ACCESS_PERM		0x00020000	/* File accessed in perm check */
+#define FAN_OPEN_EXEC_PERM	0x00040000	/* File open/exec in perm check */
 
 #define FAN_ONDIR		0x40000000	/* event occurred against dir */

Signature · 1 line

2.17.2

Jan Kara

maintainer

2018-10-16 19:54 UTC #9 lore raw

Re: [PATCH v4 3/3] fanotify: introduce new event type FAN_OPEN_EXEC_PERM

Quoted 3 lines · Matthew Bobrowski

A new event type FAN_OPEN_EXEC_PERM has been defined. This allows users to receive and grant access to files that are intending to be opened for execution.

The same note here as for FAN_OPEN_EXEC.

Quoted 7 lines

This acts in the same manor as previous permission event types, meaning that a access response is required from the application to permit further operations on the file. The event flag is set specifically when the __FMODE_EXEC flag is set within file->f_flags in the fsnotify_perm() hook.
Signed-off-by Matthew Bobrowski <[email protected]>

And a general question: Do I understand right that your audit application needs this event type? I'm asking because so far what Steve wrote me was about pattern matching of fanotify events to detect when something happens. So it's not clear to me how permission event fits into that.

Honza

Quoted 122 lines

---
 fs/notify/fanotify/fanotify.c    |  3 ++-
 fs/notify/fsnotify.c             |  2 +-
 include/linux/fanotify.h         |  3 ++-
 include/linux/fsnotify.h         | 10 ++++++----
 include/linux/fsnotify_backend.h |  7 ++++---
 include/uapi/linux/fanotify.h    |  1 +
 6 files changed, 16 insertions(+), 10 deletions(-)

fs/notify/fanotify/fanotify.c +2 -1

index 9da334d343b8..bae9a312d772 100644
@@ -212,8 +212,9 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
 	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
+	BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 12);
 
 	event_mask = fanotify_group_event_mask(iter_info, mask, data,
 						data_type);

fs/notify/fsnotify.c +1 -1

index 051e5fc0dba1..40ed97aede29 100644
@@ -402,7 +402,7 @@ static __init int fsnotify_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 24);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);
 
 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)

include/linux/fanotify.h +2 -1

index 0e07d23b6c17..614943153596 100644
@@ -42,7 +42,8 @@
 				 FAN_CLOSE | FAN_OPEN | FAN_OPEN_EXEC)
 
 /* Events that require a permission response from user */
-#define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM)
+#define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM | \
+				 FAN_OPEN_EXEC_PERM)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define FANOTIFY_EVENT_FLAGS	(FAN_EVENT_ON_CHILD | FAN_ONDIR)

include/linux/fsnotify.h +6 -4

index 1fe5ac93b252..6fb8d1fcfeaf 100644
@@ -38,12 +38,14 @@ static inline int fsnotify_perm(struct file *file, int mask)
 		return 0;
 	if (!(mask & (MAY_READ | MAY_OPEN)))
 		return 0;
-	if (mask & MAY_OPEN)
+	if (mask & MAY_OPEN) {
 		fsnotify_mask = FS_OPEN_PERM;
-	else if (mask & MAY_READ)
+
+		if (file->f_flags & __FMODE_EXEC)
+			fsnotify_mask |= FS_OPEN_EXEC_PERM;
+	} else if (mask & MAY_READ) {
 		fsnotify_mask = FS_ACCESS_PERM;
-	else
-		BUG();
+	}
 
 	ret = fsnotify_parent(path, NULL, fsnotify_mask);
 	if (ret)

include/linux/fsnotify_backend.h +4 -3

index 329ac6684326..96616651220c 100644
@@ -44,8 +44,9 @@
 #define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */
 #define FS_IN_IGNORED		0x00008000	/* last inotify event here */
 
-#define FS_OPEN_PERM		0x00010000	/* open event in an permission hook */
+#define FS_OPEN_PERM		0x00010000	/* open event in a permission hook */
 #define FS_ACCESS_PERM		0x00020000	/* access event in a permissions hook */
+#define FS_OPEN_EXEC_PERM	0x00040000	/* open/exec in a permission hook */
 
 #define FS_EXCL_UNLINK		0x04000000	/* do not send events if object is unlinked */
 #define FS_ISDIR		0x40000000	/* event occurred against dir */

@@ -64,7 +65,7 @@
 				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
 				   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
 				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM |\
-				   FS_OPEN_EXEC)
+				   FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
 
 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)

@@ -77,7 +78,7 @@
 			     FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
 			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME |\
-			     FS_OPEN_EXEC)
+			     FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \

include/uapi/linux/fanotify.h +1 -0

index da278f11ab29..e2df10c61cb1 100644
@@ -16,6 +16,7 @@
 
 #define FAN_OPEN_PERM		0x00010000	/* File open in perm check */
 #define FAN_ACCESS_PERM		0x00020000	/* File accessed in perm check */
+#define FAN_OPEN_EXEC_PERM	0x00040000	/* File open/exec in perm check */
 
 #define FAN_ONDIR		0x40000000	/* event occurred against dir */

Signature · 1 line

2.17.2

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Matthew Bobrowski

author

2018-10-17 14:27 UTC #10 lore raw

Re: [PATCH v4 3/3] fanotify: introduce new event type FAN_OPEN_EXEC_PERM

Quoted 6 lines · Jan Kara

Quoted 3 lines · Matthew Bobrowski
A new event type FAN_OPEN_EXEC_PERM has been defined. This allows users to receive and grant access to files that are intending to be opened for execution.
The same note here as for FAN_OPEN_EXEC.

Updated.

I will include the updates to this within the updated patch series.

Quoted 10 lines

Quoted 7 lines
This acts in the same manor as previous permission event types, meaning that a access response is required from the application to permit further operations on the file. The event flag is set specifically when the __FMODE_EXEC flag is set within file->f_flags in the fsnotify_perm() hook.
Signed-off-by Matthew Bobrowski <[email protected]>
And a general question: Do I understand right that your audit application needs this event type?

Yes, your understanding is correct. The application we're developing requires this event type.

Quoted 3 lines

I'm asking because so far what Steve wrote me was about pattern matching of fanotify events to detect when something happens. So it's not clear to me how permission event fits into that.

That detection for when "something happens", is precisely to do with understanding when a file is opened for execution. We use permission events within the application we're developing to either ALLOW or DENY a particular action being performed against an object. At the moment, we don't have any way to determine what actually caused a watched object to be opened, so this is to aid with that, and also help us make a better judgment how we're to respond to a particular action.

Quoted 125 lines

Quoted 122 lines

---
 fs/notify/fanotify/fanotify.c    |  3 ++-
 fs/notify/fsnotify.c             |  2 +-
 include/linux/fanotify.h         |  3 ++-
 include/linux/fsnotify.h         | 10 ++++++----
 include/linux/fsnotify_backend.h |  7 ++++---
 include/uapi/linux/fanotify.h    |  1 +
 6 files changed, 16 insertions(+), 10 deletions(-)

fs/notify/fanotify/fanotify.c +2 -1

index 9da334d343b8..bae9a312d772 100644
@@ -212,8 +212,9 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
 	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
+	BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 12);
 
 	event_mask = fanotify_group_event_mask(iter_info, mask, data,
 						data_type);

fs/notify/fsnotify.c +1 -1

index 051e5fc0dba1..40ed97aede29 100644
@@ -402,7 +402,7 @@ static __init int fsnotify_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 24);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);
 
 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)

include/linux/fanotify.h +2 -1

index 0e07d23b6c17..614943153596 100644
@@ -42,7 +42,8 @@
 				 FAN_CLOSE | FAN_OPEN | FAN_OPEN_EXEC)
 
 /* Events that require a permission response from user */
-#define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM)
+#define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM | \
+				 FAN_OPEN_EXEC_PERM)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define FANOTIFY_EVENT_FLAGS	(FAN_EVENT_ON_CHILD | FAN_ONDIR)

include/linux/fsnotify.h +6 -4

index 1fe5ac93b252..6fb8d1fcfeaf 100644
@@ -38,12 +38,14 @@ static inline int fsnotify_perm(struct file *file, int mask)
 		return 0;
 	if (!(mask & (MAY_READ | MAY_OPEN)))
 		return 0;
-	if (mask & MAY_OPEN)
+	if (mask & MAY_OPEN) {
 		fsnotify_mask = FS_OPEN_PERM;
-	else if (mask & MAY_READ)
+
+		if (file->f_flags & __FMODE_EXEC)
+			fsnotify_mask |= FS_OPEN_EXEC_PERM;
+	} else if (mask & MAY_READ) {
 		fsnotify_mask = FS_ACCESS_PERM;
-	else
-		BUG();
+	}
 
 	ret = fsnotify_parent(path, NULL, fsnotify_mask);
 	if (ret)

include/linux/fsnotify_backend.h +4 -3

index 329ac6684326..96616651220c 100644
@@ -44,8 +44,9 @@
 #define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */
 #define FS_IN_IGNORED		0x00008000	/* last inotify event here */
 
-#define FS_OPEN_PERM		0x00010000	/* open event in an permission hook */
+#define FS_OPEN_PERM		0x00010000	/* open event in a permission hook */
 #define FS_ACCESS_PERM		0x00020000	/* access event in a permissions hook */
+#define FS_OPEN_EXEC_PERM	0x00040000	/* open/exec in a permission hook */
 
 #define FS_EXCL_UNLINK		0x04000000	/* do not send events if object is unlinked */
 #define FS_ISDIR		0x40000000	/* event occurred against dir */

@@ -64,7 +65,7 @@
 				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
 				   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
 				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM |\
-				   FS_OPEN_EXEC)
+				   FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
 
 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)

@@ -77,7 +78,7 @@
 			     FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
 			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME |\
-			     FS_OPEN_EXEC)
+			     FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \

include/uapi/linux/fanotify.h +1 -0

index da278f11ab29..e2df10c61cb1 100644
@@ -16,6 +16,7 @@
 
 #define FAN_OPEN_PERM		0x00010000	/* File open in perm check */
 #define FAN_ACCESS_PERM		0x00020000	/* File accessed in perm check */
+#define FAN_OPEN_EXEC_PERM	0x00040000	/* File open/exec in perm check */
 
 #define FAN_ONDIR		0x40000000	/* event occurred against dir */

Signature · 1 line

2.17.2

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Jan Kara

maintainer

2018-10-17 19:18 UTC #11 lore raw

Re: [PATCH v4 3/3] fanotify: introduce new event type FAN_OPEN_EXEC_PERM

Quoted 10 lines · Matthew Bobrowski

Quoted 2 lines
And a general question: Do I understand right that your audit application needs this event type?
Yes, your understanding is correct. The application we're developing requires this event type.
Quoted 3 lines
I'm asking because so far what Steve wrote me was about pattern matching of fanotify events to detect when something happens. So it's not clear to me how permission event fits into that.

Quoted 7 lines

That detection for when "something happens", is precisely to do with understanding when a file is opened for execution. We use permission events within the application we're developing to either ALLOW or DENY a particular action being performed against an object. At the moment, we don't have any way to determine what actually caused a watched object to be opened, so this is to aid with that, and also help us make a better judgment how we're to respond to a particular action.

OK, understood. I just wanted to be sure I understand what you need correctly. Thanks for explanation.

Honza

Signature · 2 lines

Jan Kara <[email protected]>
SUSE Labs, CR

Amir Goldstein

reviewer Reviewed-by on the v4 series

2018-10-11 18:29 UTC #12 lore raw

In reply to Matthew Bobrowski

Quoted 39 lines · Matthew Bobrowski

Currently, the fanotify API does not provide a means for user space applications to receive events when a file has been opened specifically for execution. New event types FAN_OPEN_EXEC and FAN_OPEN_EXEC_PERM have been introduced in order to provide users this capability.
These event types, when either are explicitly requested by the user, will be returned within the event mask when a marked file object is being opened has __FMODE_EXEC set as one of the flags for open_flag.
Linux is used as an operating system in some products, with an environment that can be certified under the Common Criteria Operating System Protection Profile (OSPP). This is a formal threat model for a class of technology. It requires specific countermeasures to mitigate threats. It requires documentation to explain how a product implements these countermeasures. It requires proof via a test suite to demonstrate that the requirements are met, observed and checked by an independent qualified third party. The latest set of requirements for OSPP v4.2 can be found here:
https://www.niap-ccevs.org/Profile/Info.cfm?PPID=424&id=424
If you look on page 58, you will see the following requirement:
FPT_SRP_EXT.1 Software Restriction Policies FPT_SRP_EXT.1.1 administrator specified [selection:
file path,
file digital signature,
version,
hash,
[assignment: other characteristics]
]
This patch is to help aid in meeting this requirement.
I've also written the required updates for the man-pages project. You can find the necessary changes for these new event types within the following commit:

Quoted 8 lines

https://github.com/matthewbobrowski/man-pages/commit/d075dd8c8dfe19fccb9ea91f9550ea41b6e67334
Please note that all modifications here are based on the changes Amir has made around deprecating some of the previously exposed UAPI constants. The branch which my changes are based on can be found here:
https://github.com/amir73il/linux/tree/fanotify_api-v3

There is already a newer version merge to Jan's fsnotify branch. You should reabse on that branch, althrough I don't see any immediate merge conflicts.

Quoted 3 lines

Lastly, thanks to both Amir and Jan for their help and feedback along the way, truly appreciated.

Jan,

You may add

Reviewed-by Amir Goldstein <[email protected]>

on the series.

Thanks,
Amir.