Patch "vfs: move permission checking into notify_change() for utimes(NULL)" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message Oct 20, 2016

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2016-10-20 15:53 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

vfs: move permission checking into notify_change() for utimes(NULL)

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
vfs-move-permission-checking-into-notify_change-for-utimes-null.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From f2b20f6ee842313a0d681dbbf7f87b70291a6a3b Mon Sep 17 00:00:00 2001

From: Miklos Szeredi <[email protected]>
Date: Fri, 16 Sep 2016 12:44:20 +0200
Subject: vfs: move permission checking into notify_change() for utimes(NULL)

From: Miklos Szeredi <[email protected]>

commit f2b20f6ee842313a0d681dbbf7f87b70291a6a3b upstream.

This fixes a bug where the permission was not properly checked in overlayfs. The testcase is ltp/utimensat01.

It is also cleaner and safer to do the permission checking in the vfs helper instead of the caller.

This patch introduces an additional ia_valid flag ATTR_TOUCH (since touch(1) is the most obvious user of utimes(NULL)) that is passed into notify_change whenever the conditions for this special permission checking mode are met.

Reported-by Aihua Zhang <[email protected]>

Signed-off-by Miklos Szeredi <[email protected]>

Tested-by Aihua Zhang <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 fs/attr.c          |   15 +++++++++++++++
 fs/utimes.c        |   16 +---------------
 include/linux/fs.h |    1 +
 3 files changed, 17 insertions(+), 15 deletions(-)

fs/attr.c +15 -0

@@ -202,6 +202,21 @@ int notify_change(struct dentry * dentry
 			return -EPERM;
 	}
 
+	/*
+	 * If utimes(2) and friends are called with times == NULL (or both
+	 * times are UTIME_NOW), then we need to check for write permission
+	 */
+	if (ia_valid & ATTR_TOUCH) {
+		if (IS_IMMUTABLE(inode))
+			return -EPERM;
+
+		if (!inode_owner_or_capable(inode)) {
+			error = inode_permission(inode, MAY_WRITE);
+			if (error)
+				return error;
+		}
+	}
+
 	if ((ia_valid & ATTR_MODE)) {
 		umode_t amode = attr->ia_mode;
 		/* Flag setting protected by i_mutex */

fs/utimes.c +1 ~~-15~~

@@ -87,20 +87,7 @@ static int utimes_common(struct path *pa
 		 */
 		newattrs.ia_valid |= ATTR_TIMES_SET;
 	} else {
-		/*
-		 * If times is NULL (or both times are UTIME_NOW),
-		 * then we need to check permissions, because
-		 * inode_change_ok() won't do it.
-		 */
-		error = -EACCES;
-                if (IS_IMMUTABLE(inode))
-			goto mnt_drop_write_and_out;
-
-		if (!inode_owner_or_capable(inode)) {
-			error = inode_permission(inode, MAY_WRITE);
-			if (error)
-				goto mnt_drop_write_and_out;
-		}
+		newattrs.ia_valid |= ATTR_TOUCH;
 	}
 retry_deleg:
 	mutex_lock(&inode->i_mutex);

@@ -112,7 +99,6 @@ retry_deleg:
 			goto retry_deleg;
 	}
 
-mnt_drop_write_and_out:
 	mnt_drop_write(path->mnt);
 out:
 	return error;

include/linux/fs.h +1 -0

@@ -226,6 +226,7 @@ typedef void (dax_iodone_t)(struct buffe
 #define ATTR_KILL_PRIV	(1 << 14)
 #define ATTR_OPEN	(1 << 15) /* Truncating from open(O_TRUNC) */
 #define ATTR_TIMES_SET	(1 << 16)
+#define ATTR_TOUCH	(1 << 17)
 
 /*
  * Whiteout is represented by a char device.  The following constants define the

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/vfs-move-permission-checking-into-notify_change-for-utimes-null.patch queue-4.4/fuse-listxattr-verify-xattr-list.patch queue-4.4/fuse-invalidate-dir-dentry-after-chmod.patch queue-4.4/fuse-fix-killing-sid-in-setattr.patch