audit: show more information for entries with anonymous parents

Tracefs or debugfs were causing hundreds to thousands of null PATH records to be associated with the init_module and finit_module SYSCALL records on a few modules when the following rule was in place for startup:
-a always,exit -F arch=x86_64 -S init_module -F key=mod-load

This happens because the parent inode is not found in the task's audit_names list and hence treats it as anonymous. This gives us no information other than a numerical device number for a device that may no longer be visible upon log inspeciton, and an inode number.

Fill in the partial known pathname from the filesystem mount point to the leaf node on previously null PATH records from entries that have an anonymous parent from the child dentry using dentry_path_raw().

Make the dentry argument of __audit_inode_child() non-const so that we can take a reference to it in the case of an anonymous parent with dget() and dget_parent() to be able to later print a partial path from the host filesystem rather than null.

Since all we are given is an inode of the parent and the dentry of the child, finding the path from the mount point to the root of the filesystem is more challenging that would involve searching all vfsmounts from "/" until a matching dentry is found for that filesystem's root dentry. Even if one is found, there may be more than one mount point. At this point the gain seems marginal since knowing the filesystem type and path are a significant help in tracking down the source of the PATH records and being able to address them.

Sample output:
type=PROCTITLE msg=audit(1488317694.446:143):
proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D006E66737634 type=PATH msg=audit(1488317694.446:143): item=797 name=events/nfs4/nfs4_setclientid/format inode=15969 dev=00:09 mode=0100444 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=796 name=events/nfs4/nfs4_setclientid inode=15964 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 ... type=PATH msg=audit(1488317694.446:143): item=1 name=events/nfs4 inode=15571 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=0 name=events inode=119 dev=00:09

mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=KERN_MODULE msg=audit(1488317694.446:143): name="nfsv4" type=SYSCALL msg=audit(1488317694.446:143): arch=c000003e syscall=313 success=yes exit=0 a0=1 a1=55d5a35ce106 a2=0 a3=1 items=798 ppid=6 pid=528 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="modprobe" exe="/usr/bin/kmod" subj=system_u:system_r:insmod_t:s0 key="mod-load"

See: https://github.com/linux-audit/audit-kernel/issues/8
Test case: https://github.com/linux-audit/audit-testsuite/issues/42

Signed-off-by Richard Guy Briggs <[email protected]>

---
v4:
fix fullpath memleak
switch from log_format() to audit_log_untrustedstring() remove leading / from pathname relative to unknown mount point

v3:
fix audit_buffer leak and dname error allocation leak audit_log_name only put audit_name->dentry if it is being replaced

v2:
deconstify struct dentry*
add hex prefix to fstype

---
 include/linux/audit.h |  8 ++++----
 kernel/audit.c        | 28 +++++++++++++++++++++++++++-
 kernel/audit.h        |  1 +
 kernel/auditsc.c      |  8 +++++++-
 4 files changed, 39 insertions(+), 6 deletions(-)

include/linux/audit.h +4 -4

index af410d9..2020f1d 100644
@@ -232,7 +232,7 @@ extern void __audit_inode(struct filename *name, const
 struct dentry *dentry, unsigned int flags);
 extern void __audit_file(const struct file *);
 extern void __audit_inode_child(struct inode *parent,
-				const struct dentry *dentry,
+				struct dentry *dentry,
 				const unsigned char type);
 extern void __audit_seccomp(unsigned long syscall, long signr, int code);
 extern void __audit_ptrace(struct task_struct *t);

@@ -297,7 +297,7 @@ static inline void audit_inode_parent_hidden(struct
 filename *name, AUDIT_INODE_PARENT | AUDIT_INODE_HIDDEN);
 }
 static inline void audit_inode_child(struct inode *parent,
-				     const struct dentry *dentry,
+				     struct dentry *dentry,
 				     const unsigned char type) {
 	if (unlikely(!audit_dummy_context()))
 		__audit_inode_child(parent, dentry, type);

@@ -481,7 +481,7 @@ static inline void __audit_inode(struct filename *name,
 unsigned int flags)
 { }
 static inline void __audit_inode_child(struct inode *parent,
-					const struct dentry *dentry,
+					struct dentry *dentry,
 					const unsigned char type)
 { }
 static inline void audit_inode(struct filename *name,

@@ -495,7 +495,7 @@ static inline void audit_inode_parent_hidden(struct
 filename *name, const struct dentry *dentry)
 { }
 static inline void audit_inode_child(struct inode *parent,
-				     const struct dentry *dentry,
+				     struct dentry *dentry,
 				     const unsigned char type)
 { }
 static inline void audit_core_dumps(long signr)

kernel/audit.c +27 -1

index 227db99..0c8d5a8 100644
@@ -72,6 +72,7 @@
 #include <linux/freezer.h>
 #include <linux/pid_namespace.h>
 #include <net/netns/generic.h>
+#include <linux/dcache.h>
 
 #include "audit.h"
 

@@ -2056,6 +2057,10 @@ void audit_copy_inode(struct audit_names *name,
 const struct dentry *dentry, name->gid   = inode->i_gid;
 	name->rdev  = inode->i_rdev;
 	security_inode_getsecid(inode, &name->osid);
+	if (name->dentry) {
+		dput(name->dentry);
+		name->dentry = NULL;
+	}
 	audit_copy_fcaps(name, dentry);
 }
 

@@ -2097,8 +2102,29 @@ void audit_log_name(struct audit_context *context,
 struct audit_names *n, audit_log_n_untrustedstring(ab, n->name->name,
 						    n->name_len);
 		}
-	} else
+	} else if (n->dentry) {
+		char *fullpath;
+		const char *fullpathp = NULL;
+
+		fullpath = kmalloc(PATH_MAX, GFP_KERNEL);
+		if (fullpath) {
+			fullpathp = dentry_path_raw(n->dentry, fullpath, PATH_MAX);
+			if (IS_ERR(fullpathp)) {
+				fullpathp = NULL;
+			} else {
+				while (*fullpathp == '/')
+					fullpathp++;
+				if (*fullpathp == 0)
+					fullpathp = NULL;
+			}
+		}
+		audit_log_format(ab, " name=");
+		audit_log_untrustedstring(ab, fullpathp ?: "?");
+		if (fullpath)
+			kfree(fullpath);
+	} else {
 		audit_log_format(ab, " name=(null)");
+	}
 
 	if (n->ino != AUDIT_INO_UNSET)
 		audit_log_format(ab, " inode=%lu"

kernel/audit.h +1 -0

index af5bc59..81f6865 100644
@@ -85,6 +85,7 @@ struct audit_names {
 
 	unsigned long		ino;
 	dev_t			dev;
+	struct dentry		*dentry;
 	umode_t			mode;
 	kuid_t			uid;
 	kgid_t			gid;

kernel/auditsc.c +7 -1

index e80459f..b73ede0 100644
@@ -75,6 +75,7 @@
 #include <linux/uaccess.h>
 #include <linux/fsnotify_backend.h>
 #include <uapi/linux/limits.h>
+#include <linux/dcache.h>
 
 #include "audit.h"
 

@@ -882,6 +883,8 @@ static inline void audit_free_names(struct
 audit_context *context) list_del(&n->list);
 		if (n->name)
 			putname(n->name);
+		if (n->dentry)
+			dput(n->dentry);
 		if (n->should_free)
 			kfree(n);
 	}

@@ -1862,7 +1865,7 @@ void __audit_file(const struct file *file)
  * unsuccessful attempts.
  */
 void __audit_inode_child(struct inode *parent,
-			 const struct dentry *dentry,
+			 struct dentry *dentry,
 			 const unsigned char type)
 {
 	struct audit_context *context = current->audit_context;

@@ -1941,6 +1944,7 @@ void __audit_inode_child(struct inode *parent,
 		if (!n)
 			return;
 		audit_copy_inode(n, NULL, parent);
+		n->dentry = dget_parent(dentry);
 	}
 
 	if (!found_child) {

@@ -1962,6 +1966,8 @@ void __audit_inode_child(struct inode *parent,
 		audit_copy_inode(found_child, dentry, inode);
 	else
 		found_child->ino = AUDIT_INO_UNSET;
+	if (!found_parent)
+		found_child->dentry = dget(dentry);
 }
 EXPORT_SYMBOL_GPL(__audit_inode_child);

Quoted 45 lines · EST Richard Guy Briggs

Tracefs or debugfs were causing hundreds to thousands of null PATH records to be associated with the init_module and finit_module SYSCALL records on a few modules when the following rule was in place for startup:
-a always,exit -F arch=x86_64 -S init_module -F key=mod-load

This happens because the parent inode is not found in the task's audit_names list and hence treats it as anonymous. This gives us no information other than a numerical device number for a device that may no longer be visible upon log inspeciton, and an inode number.

Fill in the partial known pathname from the filesystem mount point to the leaf node on previously null PATH records from entries that have an anonymous parent from the child dentry using dentry_path_raw().

Make the dentry argument of __audit_inode_child() non-const so that we can take a reference to it in the case of an anonymous parent with dget() and dget_parent() to be able to later print a partial path from the host filesystem rather than null.

Since all we are given is an inode of the parent and the dentry of the child, finding the path from the mount point to the root of the filesystem is more challenging that would involve searching all vfsmounts from "/" until a matching dentry is found for that filesystem's root dentry. Even if one is found, there may be more than one mount point. At this point the gain seems marginal since knowing the filesystem type and path are a significant help in tracking down the source of the PATH records and being able to address them.

Sample output:
type=PROCTITLE msg=audit(1488317694.446:143):
proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D006E66737634 type=PATH msg=audit(1488317694.446:143): item=797 name=events/nfs4/nfs4_setclientid/format inode=15969 dev=00:09 mode=0100444 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=796 name=events/nfs4/nfs4_setclientid inode=15964 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 ... type=PATH msg=audit(1488317694.446:143): item=1 name=events/nfs4 inode=15571 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=0 name=events inode=119 dev=00:09

Quoted 8 lines

mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=KERN_MODULE msg=audit(1488317694.446:143): name="nfsv4" type=SYSCALL msg=audit(1488317694.446:143): arch=c000003e syscall=313 success=yes exit=0 a0=1 a1=55d5a35ce106 a2=0 a3=1 items=798 ppid=6 pid=528 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="modprobe" exe="/usr/bin/kmod" subj=system_u:system_r:insmod_t:s0 key="mod-load"

Thanks for the samples, but the event above fails the ausearch-test test suite. The "name" field in the PATH record is not properly escaped.

-Steve

Quoted 168 lines

See: https://github.com/linux-audit/audit-kernel/issues/8
Test case: https://github.com/linux-audit/audit-testsuite/issues/42

Signed-off-by Richard Guy Briggs <[email protected]>

---
v4:
fix fullpath memleak
switch from log_format() to audit_log_untrustedstring() remove leading / from pathname relative to unknown mount point

v3:
fix audit_buffer leak and dname error allocation leak audit_log_name only put audit_name->dentry if it is being replaced

v2:
deconstify struct dentry*
add hex prefix to fstype

---
 include/linux/audit.h |  8 ++++----
 kernel/audit.c        | 28 +++++++++++++++++++++++++++-
 kernel/audit.h        |  1 +
 kernel/auditsc.c      |  8 +++++++-
 4 files changed, 39 insertions(+), 6 deletions(-)

include/linux/audit.h +4 -4

index af410d9..2020f1d 100644
@@ -232,7 +232,7 @@ extern void __audit_inode(struct filename *name, const
 struct dentry *dentry, unsigned int flags);
 extern void __audit_file(const struct file *);
 extern void __audit_inode_child(struct inode *parent,
-				const struct dentry *dentry,
+				struct dentry *dentry,
 				const unsigned char type);
 extern void __audit_seccomp(unsigned long syscall, long signr, int code);
 extern void __audit_ptrace(struct task_struct *t);

@@ -297,7 +297,7 @@ static inline void audit_inode_parent_hidden(struct
 filename *name, AUDIT_INODE_PARENT | AUDIT_INODE_HIDDEN);
 }
 static inline void audit_inode_child(struct inode *parent,
-				     const struct dentry *dentry,
+				     struct dentry *dentry,
 				     const unsigned char type) {
 	if (unlikely(!audit_dummy_context()))
 		__audit_inode_child(parent, dentry, type);

@@ -481,7 +481,7 @@ static inline void __audit_inode(struct filename *name,
 unsigned int flags)
 { }
 static inline void __audit_inode_child(struct inode *parent,
-					const struct dentry *dentry,
+					struct dentry *dentry,
 					const unsigned char type)
 { }
 static inline void audit_inode(struct filename *name,

@@ -495,7 +495,7 @@ static inline void audit_inode_parent_hidden(struct
 filename *name, const struct dentry *dentry)
 { }
 static inline void audit_inode_child(struct inode *parent,
-				     const struct dentry *dentry,
+				     struct dentry *dentry,
 				     const unsigned char type)
 { }
 static inline void audit_core_dumps(long signr)

kernel/audit.c +27 -1

index 227db99..0c8d5a8 100644
@@ -72,6 +72,7 @@
 #include <linux/freezer.h>
 #include <linux/pid_namespace.h>
 #include <net/netns/generic.h>
+#include <linux/dcache.h>
 
 #include "audit.h"
 

@@ -2056,6 +2057,10 @@ void audit_copy_inode(struct audit_names *name,
 const struct dentry *dentry, name->gid   = inode->i_gid;
 	name->rdev  = inode->i_rdev;
 	security_inode_getsecid(inode, &name->osid);
+	if (name->dentry) {
+		dput(name->dentry);
+		name->dentry = NULL;
+	}
 	audit_copy_fcaps(name, dentry);
 }
 

@@ -2097,8 +2102,29 @@ void audit_log_name(struct audit_context *context,
 struct audit_names *n, audit_log_n_untrustedstring(ab, n->name->name,
 						    n->name_len);
 		}
-	} else
+	} else if (n->dentry) {
+		char *fullpath;
+		const char *fullpathp = NULL;
+
+		fullpath = kmalloc(PATH_MAX, GFP_KERNEL);
+		if (fullpath) {
+			fullpathp = dentry_path_raw(n->dentry, fullpath, PATH_MAX);
+			if (IS_ERR(fullpathp)) {
+				fullpathp = NULL;
+			} else {
+				while (*fullpathp == '/')
+					fullpathp++;
+				if (*fullpathp == 0)
+					fullpathp = NULL;
+			}
+		}
+		audit_log_format(ab, " name=");
+		audit_log_untrustedstring(ab, fullpathp ?: "?");
+		if (fullpath)
+			kfree(fullpath);
+	} else {
 		audit_log_format(ab, " name=(null)");
+	}
 
 	if (n->ino != AUDIT_INO_UNSET)
 		audit_log_format(ab, " inode=%lu"

kernel/audit.h +1 -0

index af5bc59..81f6865 100644
@@ -85,6 +85,7 @@ struct audit_names {
 
 	unsigned long		ino;
 	dev_t			dev;
+	struct dentry		*dentry;
 	umode_t			mode;
 	kuid_t			uid;
 	kgid_t			gid;

kernel/auditsc.c +5 -1

index e80459f..b73ede0 100644
@@ -75,6 +75,7 @@
 #include <linux/uaccess.h>
 #include <linux/fsnotify_backend.h>
 #include <uapi/linux/limits.h>
+#include <linux/dcache.h>
 
 #include "audit.h"
 

@@ -882,6 +883,8 @@ static inline void audit_free_names(struct
 audit_context *context) list_del(&n->list);
 		if (n->name)
 			putname(n->name);
+		if (n->dentry)
+			dput(n->dentry);
 		if (n->should_free)
 			kfree(n);
 	}

@@ -1862,7 +1865,7 @@ void __audit_file(const struct file *file)
  * unsuccessful attempts.
  */
 void __audit_inode_child(struct inode *parent,
-			 const struct dentry *dentry,
+			 struct dentry *dentry,
 			 const unsigned char type)
 {
 	struct audit_context *context = current->audit_context;

@@ -1941,6 +1944,7 @@ void __audit_inode_child(struct inode *parent,
 		if (!n)
 			return;
 		audit_copy_inode(n, NULL, parent);
+		n->dentry = dget_parent(dentry);
 	}
 

kernel/auditsc.c void __audit_inode_child(struct inode *parent, · line 1972

Quoted 9 lines

kernel/auditsc.c +2 -0

 	if (!found_child) {

@@ -1962,6 +1966,8 @@ void __audit_inode_child(struct inode *parent,
 		audit_copy_inode(found_child, dentry, inode);
 	else
 		found_child->ino = AUDIT_INO_UNSET;
+	if (!found_parent)
+		found_child->dentry = dget(dentry);
 }
 EXPORT_SYMBOL_GPL(__audit_inode_child);

Quoted 46 lines · Steve Grubb

Quoted 45 lines · EST Richard Guy Briggs

Tracefs or debugfs were causing hundreds to thousands of null PATH records to be associated with the init_module and finit_module SYSCALL records on a few modules when the following rule was in place for startup:
-a always,exit -F arch=x86_64 -S init_module -F key=mod-load

This happens because the parent inode is not found in the task's audit_names list and hence treats it as anonymous. This gives us no information other than a numerical device number for a device that may no longer be visible upon log inspeciton, and an inode number.

Fill in the partial known pathname from the filesystem mount point to the leaf node on previously null PATH records from entries that have an anonymous parent from the child dentry using dentry_path_raw().

Make the dentry argument of __audit_inode_child() non-const so that we can take a reference to it in the case of an anonymous parent with dget() and dget_parent() to be able to later print a partial path from the host filesystem rather than null.

Since all we are given is an inode of the parent and the dentry of the child, finding the path from the mount point to the root of the filesystem is more challenging that would involve searching all vfsmounts from "/" until a matching dentry is found for that filesystem's root dentry. Even if one is found, there may be more than one mount point. At this point the gain seems marginal since knowing the filesystem type and path are a significant help in tracking down the source of the PATH records and being able to address them.

Sample output:
type=PROCTITLE msg=audit(1488317694.446:143):
proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D006E66737634 type=PATH msg=audit(1488317694.446:143): item=797 name=events/nfs4/nfs4_setclientid/format inode=15969 dev=00:09 mode=0100444 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=796 name=events/nfs4/nfs4_setclientid inode=15964 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 ... type=PATH msg=audit(1488317694.446:143): item=1 name=events/nfs4 inode=15571 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=0 name=events inode=119 dev=00:09

Quoted 8 lines

Quoted 8 lines

mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=KERN_MODULE msg=audit(1488317694.446:143): name="nfsv4" type=SYSCALL msg=audit(1488317694.446:143): arch=c000003e syscall=313 success=yes exit=0 a0=1 a1=55d5a35ce106 a2=0 a3=1 items=798 ppid=6 pid=528 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="modprobe" exe="/usr/bin/kmod" subj=system_u:system_r:insmod_t:s0 key="mod-load"

Quoted 2 lines

Thanks for the samples, but the event above fails the ausearch-test test suite. The "name" field in the PATH record is not properly escaped.

Let me re-run the ausearch-test on the log file from the machine in question... I don't remember if I copied the above from a recent run, or just hand-edited the output to update it. It should be fine since it was updated to now run through audit_log_untrustedstring().

Quoted 170 lines

-Steve

Quoted 168 lines

See: https://github.com/linux-audit/audit-kernel/issues/8
Test case: https://github.com/linux-audit/audit-testsuite/issues/42

Signed-off-by Richard Guy Briggs <[email protected]>

---
v4:
fix fullpath memleak
switch from log_format() to audit_log_untrustedstring() remove leading / from pathname relative to unknown mount point

v3:
fix audit_buffer leak and dname error allocation leak audit_log_name only put audit_name->dentry if it is being replaced

v2:
deconstify struct dentry*
add hex prefix to fstype

---
 include/linux/audit.h |  8 ++++----
 kernel/audit.c        | 28 +++++++++++++++++++++++++++-
 kernel/audit.h        |  1 +
 kernel/auditsc.c      |  8 +++++++-
 4 files changed, 39 insertions(+), 6 deletions(-)

include/linux/audit.h +4 -4

index af410d9..2020f1d 100644
@@ -232,7 +232,7 @@ extern void __audit_inode(struct filename *name, const
 struct dentry *dentry, unsigned int flags);
 extern void __audit_file(const struct file *);
 extern void __audit_inode_child(struct inode *parent,
-				const struct dentry *dentry,
+				struct dentry *dentry,
 				const unsigned char type);
 extern void __audit_seccomp(unsigned long syscall, long signr, int code);
 extern void __audit_ptrace(struct task_struct *t);

@@ -297,7 +297,7 @@ static inline void audit_inode_parent_hidden(struct
 filename *name, AUDIT_INODE_PARENT | AUDIT_INODE_HIDDEN);
 }
 static inline void audit_inode_child(struct inode *parent,
-				     const struct dentry *dentry,
+				     struct dentry *dentry,
 				     const unsigned char type) {
 	if (unlikely(!audit_dummy_context()))
 		__audit_inode_child(parent, dentry, type);

@@ -481,7 +481,7 @@ static inline void __audit_inode(struct filename *name,
 unsigned int flags)
 { }
 static inline void __audit_inode_child(struct inode *parent,
-					const struct dentry *dentry,
+					struct dentry *dentry,
 					const unsigned char type)
 { }
 static inline void audit_inode(struct filename *name,

@@ -495,7 +495,7 @@ static inline void audit_inode_parent_hidden(struct
 filename *name, const struct dentry *dentry)
 { }
 static inline void audit_inode_child(struct inode *parent,
-				     const struct dentry *dentry,
+				     struct dentry *dentry,
 				     const unsigned char type)
 { }
 static inline void audit_core_dumps(long signr)

kernel/audit.c +27 -1

index 227db99..0c8d5a8 100644
@@ -72,6 +72,7 @@
 #include <linux/freezer.h>
 #include <linux/pid_namespace.h>
 #include <net/netns/generic.h>
+#include <linux/dcache.h>
 
 #include "audit.h"
 

@@ -2056,6 +2057,10 @@ void audit_copy_inode(struct audit_names *name,
 const struct dentry *dentry, name->gid   = inode->i_gid;
 	name->rdev  = inode->i_rdev;
 	security_inode_getsecid(inode, &name->osid);
+	if (name->dentry) {
+		dput(name->dentry);
+		name->dentry = NULL;
+	}
 	audit_copy_fcaps(name, dentry);
 }
 

@@ -2097,8 +2102,29 @@ void audit_log_name(struct audit_context *context,
 struct audit_names *n, audit_log_n_untrustedstring(ab, n->name->name,
 						    n->name_len);
 		}
-	} else
+	} else if (n->dentry) {
+		char *fullpath;
+		const char *fullpathp = NULL;
+
+		fullpath = kmalloc(PATH_MAX, GFP_KERNEL);
+		if (fullpath) {
+			fullpathp = dentry_path_raw(n->dentry, fullpath, PATH_MAX);
+			if (IS_ERR(fullpathp)) {
+				fullpathp = NULL;
+			} else {
+				while (*fullpathp == '/')
+					fullpathp++;
+				if (*fullpathp == 0)
+					fullpathp = NULL;
+			}
+		}
+		audit_log_format(ab, " name=");
+		audit_log_untrustedstring(ab, fullpathp ?: "?");
+		if (fullpath)
+			kfree(fullpath);
+	} else {
 		audit_log_format(ab, " name=(null)");
+	}
 
 	if (n->ino != AUDIT_INO_UNSET)
 		audit_log_format(ab, " inode=%lu"

kernel/audit.h +1 -0

index af5bc59..81f6865 100644
@@ -85,6 +85,7 @@ struct audit_names {
 
 	unsigned long		ino;
 	dev_t			dev;
+	struct dentry		*dentry;
 	umode_t			mode;
 	kuid_t			uid;
 	kgid_t			gid;

kernel/auditsc.c +5 -1

index e80459f..b73ede0 100644
@@ -75,6 +75,7 @@
 #include <linux/uaccess.h>
 #include <linux/fsnotify_backend.h>
 #include <uapi/linux/limits.h>
+#include <linux/dcache.h>
 
 #include "audit.h"
 

@@ -882,6 +883,8 @@ static inline void audit_free_names(struct
 audit_context *context) list_del(&n->list);
 		if (n->name)
 			putname(n->name);
+		if (n->dentry)
+			dput(n->dentry);
 		if (n->should_free)
 			kfree(n);
 	}

@@ -1862,7 +1865,7 @@ void __audit_file(const struct file *file)
  * unsuccessful attempts.
  */
 void __audit_inode_child(struct inode *parent,
-			 const struct dentry *dentry,
+			 struct dentry *dentry,
 			 const unsigned char type)
 {
 	struct audit_context *context = current->audit_context;

@@ -1941,6 +1944,7 @@ void __audit_inode_child(struct inode *parent,
 		if (!n)
 			return;
 		audit_copy_inode(n, NULL, parent);
+		n->dentry = dget_parent(dentry);
 	}
 

Quoted 9 lines

kernel/auditsc.c void __audit_inode_child(struct inode *parent, · line 1972

Quoted 9 lines

kernel/auditsc.c +2 -0

 	if (!found_child) {

@@ -1962,6 +1966,8 @@ void __audit_inode_child(struct inode *parent,
 		audit_copy_inode(found_child, dentry, inode);
 	else
 		found_child->ino = AUDIT_INO_UNSET;
+	if (!found_parent)
+		found_child->dentry = dget(dentry);
 }
 EXPORT_SYMBOL_GPL(__audit_inode_child);

- RGB

Quoted 45 lines · EST Richard Guy Briggs

Tracefs or debugfs were causing hundreds to thousands of null PATH records to be associated with the init_module and finit_module SYSCALL records on a few modules when the following rule was in place for startup:
-a always,exit -F arch=x86_64 -S init_module -F key=mod-load

This happens because the parent inode is not found in the task's audit_names list and hence treats it as anonymous. This gives us no information other than a numerical device number for a device that may no longer be visible upon log inspeciton, and an inode number.

Fill in the partial known pathname from the filesystem mount point to the leaf node on previously null PATH records from entries that have an anonymous parent from the child dentry using dentry_path_raw().

Make the dentry argument of __audit_inode_child() non-const so that we can take a reference to it in the case of an anonymous parent with dget() and dget_parent() to be able to later print a partial path from the host filesystem rather than null.

Since all we are given is an inode of the parent and the dentry of the child, finding the path from the mount point to the root of the filesystem is more challenging that would involve searching all vfsmounts from "/" until a matching dentry is found for that filesystem's root dentry. Even if one is found, there may be more than one mount point. At this point the gain seems marginal since knowing the filesystem type and path are a significant help in tracking down the source of the PATH records and being able to address them.

Sample output:
type=PROCTITLE msg=audit(1488317694.446:143):
proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D006E66737634 type=PATH msg=audit(1488317694.446:143): item=797 name=events/nfs4/nfs4_setclientid/format inode=15969 dev=00:09 mode=0100444 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=796 name=events/nfs4/nfs4_setclientid inode=15964 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 ... type=PATH msg=audit(1488317694.446:143): item=1 name=events/nfs4 inode=15571 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=0 name=events inode=119 dev=00:09

Quoted 8 lines

mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=KERN_MODULE msg=audit(1488317694.446:143): name="nfsv4" type=SYSCALL msg=audit(1488317694.446:143): arch=c000003e syscall=313 success=yes exit=0 a0=1 a1=55d5a35ce106 a2=0 a3=1 items=798 ppid=6 pid=528 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="modprobe" exe="/usr/bin/kmod" subj=system_u:system_r:insmod_t:s0 key="mod-load"

Thanks for the samples, but the event above fails the ausearch-test test suite. The "name" field in the PATH record is not properly escaped.

-Steve

Quoted 168 lines

See: https://github.com/linux-audit/audit-kernel/issues/8
Test case: https://github.com/linux-audit/audit-testsuite/issues/42

Signed-off-by Richard Guy Briggs <[email protected]>

---
v4:
fix fullpath memleak
switch from log_format() to audit_log_untrustedstring() remove leading / from pathname relative to unknown mount point

v3:
fix audit_buffer leak and dname error allocation leak audit_log_name only put audit_name->dentry if it is being replaced

v2:
deconstify struct dentry*
add hex prefix to fstype

---
 include/linux/audit.h |  8 ++++----
 kernel/audit.c        | 28 +++++++++++++++++++++++++++-
 kernel/audit.h        |  1 +
 kernel/auditsc.c      |  8 +++++++-
 4 files changed, 39 insertions(+), 6 deletions(-)

include/linux/audit.h +4 -4

index af410d9..2020f1d 100644
@@ -232,7 +232,7 @@ extern void __audit_inode(struct filename *name, const
 struct dentry *dentry, unsigned int flags);
 extern void __audit_file(const struct file *);
 extern void __audit_inode_child(struct inode *parent,
-				const struct dentry *dentry,
+				struct dentry *dentry,
 				const unsigned char type);
 extern void __audit_seccomp(unsigned long syscall, long signr, int code);
 extern void __audit_ptrace(struct task_struct *t);

@@ -297,7 +297,7 @@ static inline void audit_inode_parent_hidden(struct
 filename *name, AUDIT_INODE_PARENT | AUDIT_INODE_HIDDEN);
 }
 static inline void audit_inode_child(struct inode *parent,
-				     const struct dentry *dentry,
+				     struct dentry *dentry,
 				     const unsigned char type) {
 	if (unlikely(!audit_dummy_context()))
 		__audit_inode_child(parent, dentry, type);

@@ -481,7 +481,7 @@ static inline void __audit_inode(struct filename *name,
 unsigned int flags)
 { }
 static inline void __audit_inode_child(struct inode *parent,
-					const struct dentry *dentry,
+					struct dentry *dentry,
 					const unsigned char type)
 { }
 static inline void audit_inode(struct filename *name,

@@ -495,7 +495,7 @@ static inline void audit_inode_parent_hidden(struct
 filename *name, const struct dentry *dentry)
 { }
 static inline void audit_inode_child(struct inode *parent,
-				     const struct dentry *dentry,
+				     struct dentry *dentry,
 				     const unsigned char type)
 { }
 static inline void audit_core_dumps(long signr)

kernel/audit.c +27 -1

index 227db99..0c8d5a8 100644
@@ -72,6 +72,7 @@
 #include <linux/freezer.h>
 #include <linux/pid_namespace.h>
 #include <net/netns/generic.h>
+#include <linux/dcache.h>
 
 #include "audit.h"
 

@@ -2056,6 +2057,10 @@ void audit_copy_inode(struct audit_names *name,
 const struct dentry *dentry, name->gid   = inode->i_gid;
 	name->rdev  = inode->i_rdev;
 	security_inode_getsecid(inode, &name->osid);
+	if (name->dentry) {
+		dput(name->dentry);
+		name->dentry = NULL;
+	}
 	audit_copy_fcaps(name, dentry);
 }
 

@@ -2097,8 +2102,29 @@ void audit_log_name(struct audit_context *context,
 struct audit_names *n, audit_log_n_untrustedstring(ab, n->name->name,
 						    n->name_len);
 		}
-	} else
+	} else if (n->dentry) {
+		char *fullpath;
+		const char *fullpathp = NULL;
+
+		fullpath = kmalloc(PATH_MAX, GFP_KERNEL);
+		if (fullpath) {
+			fullpathp = dentry_path_raw(n->dentry, fullpath, PATH_MAX);
+			if (IS_ERR(fullpathp)) {
+				fullpathp = NULL;
+			} else {
+				while (*fullpathp == '/')
+					fullpathp++;
+				if (*fullpathp == 0)
+					fullpathp = NULL;
+			}
+		}
+		audit_log_format(ab, " name=");
+		audit_log_untrustedstring(ab, fullpathp ?: "?");
+		if (fullpath)
+			kfree(fullpath);
+	} else {
 		audit_log_format(ab, " name=(null)");
+	}
 
 	if (n->ino != AUDIT_INO_UNSET)
 		audit_log_format(ab, " inode=%lu"

kernel/audit.h +1 -0

index af5bc59..81f6865 100644
@@ -85,6 +85,7 @@ struct audit_names {
 
 	unsigned long		ino;
 	dev_t			dev;
+	struct dentry		*dentry;
 	umode_t			mode;
 	kuid_t			uid;
 	kgid_t			gid;

kernel/auditsc.c +5 -1

index e80459f..b73ede0 100644
@@ -75,6 +75,7 @@
 #include <linux/uaccess.h>
 #include <linux/fsnotify_backend.h>
 #include <uapi/linux/limits.h>
+#include <linux/dcache.h>
 
 #include "audit.h"
 

@@ -882,6 +883,8 @@ static inline void audit_free_names(struct
 audit_context *context) list_del(&n->list);
 		if (n->name)
 			putname(n->name);
+		if (n->dentry)
+			dput(n->dentry);
 		if (n->should_free)
 			kfree(n);
 	}

@@ -1862,7 +1865,7 @@ void __audit_file(const struct file *file)
  * unsuccessful attempts.
  */
 void __audit_inode_child(struct inode *parent,
-			 const struct dentry *dentry,
+			 struct dentry *dentry,
 			 const unsigned char type)
 {
 	struct audit_context *context = current->audit_context;

@@ -1941,6 +1944,7 @@ void __audit_inode_child(struct inode *parent,
 		if (!n)
 			return;
 		audit_copy_inode(n, NULL, parent);
+		n->dentry = dget_parent(dentry);
 	}
 

kernel/auditsc.c void __audit_inode_child(struct inode *parent, · line 1972

Quoted 9 lines

kernel/auditsc.c +2 -0

 	if (!found_child) {

@@ -1962,6 +1966,8 @@ void __audit_inode_child(struct inode *parent,
 		audit_copy_inode(found_child, dentry, inode);
 	else
 		found_child->ino = AUDIT_INO_UNSET;
+	if (!found_parent)
+		found_child->dentry = dget(dentry);
 }
 EXPORT_SYMBOL_GPL(__audit_inode_child);

More than one filesystem was causing hundreds to thousands of null PATH records to be associated with the *init_module SYSCALL records on a few modules with corresponding audit syscall rules.

This patchset adds extra information to those PATH records to provide insight into what is generating them, including a partial pathname, fstype field, and two new filetypes that indicate the pathname isn't anchored at the root of the task's root filesystem.

Richard Guy Briggs (3):
audit: show partial pathname for entries with anonymous parents
audit: append new fstype field for anonymous PATH records
audit: add new filetypes CREATE_ANON and PARENT_ANON

Quoted 9 lines · Richard Guy Briggs

More than one filesystem was causing hundreds to thousands of null PATH records to be associated with the *init_module SYSCALL records on a few modules with corresponding audit syscall rules.

This patchset adds extra information to those PATH records to provide insight into what is generating them, including a partial pathname, fstype field, and two new filetypes that indicate the pathname isn't anchored at the root of the task's root filesystem.

Quoted 4 lines

Richard Guy Briggs (3):
audit: show partial pathname for entries with anonymous parents
audit: append new fstype field for anonymous PATH records
audit: add new filetypes CREATE_ANON and PARENT_ANON

The more I look at this, the more I prefer your original approach that prefixed the relative pathname with the fstype. Yes, I do realize that you sort of work around that by including the fstype as a new field in the PATH records, but we're still stuck with those odd relative/un-rooted name fields.

Further, I don't recall ever hearing a good reason why the original approach wasn't acceptable to Steve's userspace. I know he did make some very last minute hand-wavy comments, but none of those made any sense to me; I don't understand why Steve's audit record parser is even looking in the pathname string.

I'm going to park these patches in limbo for the time being.

paul moore

Quoted 15 lines · Paul Moore

Quoted 9 lines · Richard Guy Briggs

More than one filesystem was causing hundreds to thousands of null PATH records to be associated with the *init_module SYSCALL records on a few modules with corresponding audit syscall rules.

This patchset adds extra information to those PATH records to provide insight into what is generating them, including a partial pathname, fstype field, and two new filetypes that indicate the pathname isn't anchored at the root of the task's root filesystem.

Quoted 4 lines

Richard Guy Briggs (3):
audit: show partial pathname for entries with anonymous parents
audit: append new fstype field for anonymous PATH records
audit: add new filetypes CREATE_ANON and PARENT_ANON

Quoted 5 lines

The more I look at this, the more I prefer your original approach that prefixed the relative pathname with the fstype. Yes, I do realize that you sort of work around that by including the fstype as a new field in the PATH records, but we're still stuck with those odd relative/un-rooted name fields.

They are signalled as being unrooted by the ANON filetypes. And now that you mention it, should fail the ausearch-test since it isn't a "full path", as claimed is necessary in ghak70 (so I don't see why the KERN_MODULE name= record/field fails that test).

Quoted 7 lines

Further, I don't recall ever hearing a good reason why the original approach wasn't acceptable to Steve's userspace. I know he did make some very last minute hand-wavy comments, but none of those made any sense to me; I don't understand why Steve's audit record parser is even looking in the pathname string.

I'm going to park these patches in limbo for the time being.

Can you give me an idea how long that might be?