Patch "xfs: Fix xfs_attr_leafblock definition" has been added to the 4.1-stable tree

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

xfs: Fix xfs_attr_leafblock definition

to the 4.1-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:
xfs-fix-xfs_attr_leafblock-definition.patch
and it can be found in the queue-4.1 subdirectory.

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

From: Jan Kara <[email protected]>
Date: Wed, 19 Aug 2015 10:34:32 +1000
Subject: xfs: Fix xfs_attr_leafblock definition

From: Jan Kara <[email protected]>

commit ffeecc5213024ae663377b442eedcfbacf6d0c5d upstream.

struct xfs_attr_leafblock contains 'entries' array which is declared with size 1 altough it can in fact contain much more entries. Since this array is followed by further struct members, gcc (at least in version 4.8.3) thinks that the array has the fixed size of 1 element and thus may optimize away all accesses beyond the end of array resulting in non-working code. This problem was only observed with userspace code in xfsprogs, however it's better to be safe in kernel as well and have matching kernel and xfsprogs definitions.

---
 fs/xfs/libxfs/xfs_da_format.h |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

@@ -680,8 +680,15 @@ typedef struct xfs_attr_leaf_name_remote
 typedef struct xfs_attr_leafblock {
 	xfs_attr_leaf_hdr_t	hdr;	/* constant-structure header block */
 	xfs_attr_leaf_entry_t	entries[1];	/* sorted on key, not name */
-	xfs_attr_leaf_name_local_t namelist;	/* grows from bottom of buf */
-	xfs_attr_leaf_name_remote_t valuelist;	/* grows from bottom of buf */
+	/*
+	 * The rest of the block contains the following structures after the
+	 * leaf entries, growing from the bottom up. The variables are never
+	 * referenced and definining them can actually make gcc optimize away
+	 * accesses to the 'entries' array above index 0 so don't do that.
+	 *
+	 * xfs_attr_leaf_name_local_t namelist;
+	 * xfs_attr_leaf_name_remote_t valuelist;
+	 */
 } xfs_attr_leafblock_t;
 
 /*

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

queue-4.1/xfs-fix-file-type-directory-corruption-for-btree-directories.patch queue-4.1/xfs-fix-xfs_attr_leafblock-definition.patch