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[PATCH 3.14 14/25] btrfs: fix use after free iterating extrefs

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3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chris Mason <clm@fb.com>

commit dc6c5fb3b514221f2e9d21ee626a9d95d3418dff upstream.

The code for btrfs inode-resolve has never worked properly for
files with enough hard links to trigger extrefs.  It was trying to
get the leaf out of a path after freeing the path:

	btrfs_release_path(path);
	leaf = path->nodes[0];
	item_size = btrfs_item_size_nr(leaf, slot);

The fix here is to use the extent buffer we cloned just a little higher
up to avoid deadlocks caused by using the leaf in the path.

Signed-off-by: Chris Mason <clm@fb.com>
cc: Mark Fasheh <mfasheh@suse.de>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Mark Fasheh <mfasheh@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/btrfs/backref.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -1692,7 +1692,6 @@ static int iterate_inode_extrefs(u64 inu
 	int found = 0;
 	struct extent_buffer *eb;
 	struct btrfs_inode_extref *extref;
-	struct extent_buffer *leaf;
 	u32 item_size;
 	u32 cur_offset;
 	unsigned long ptr;
@@ -1720,9 +1719,8 @@ static int iterate_inode_extrefs(u64 inu
 		btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
 		btrfs_release_path(path);
 
-		leaf = path->nodes[0];
-		item_size = btrfs_item_size_nr(leaf, slot);
-		ptr = btrfs_item_ptr_offset(leaf, slot);
+		item_size = btrfs_item_size_nr(eb, slot);
+		ptr = btrfs_item_ptr_offset(eb, slot);
 		cur_offset = 0;
 
 		while (cur_offset < item_size) {
@@ -1736,7 +1734,7 @@ static int iterate_inode_extrefs(u64 inu
 			if (ret)
 				break;
 
-			cur_offset += btrfs_inode_extref_name_len(leaf, extref);
+			cur_offset += btrfs_inode_extref_name_len(eb, extref);
 			cur_offset += sizeof(*extref);
 		}
 		btrfs_tree_read_unlock_blocking(eb);


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[PATCH 3.14 00/25] 3.14.56-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 02/25] af_unix: Convert the unix_sk macro to an inline function for type safety Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 24/25] sched/preempt: Rename PREEMPT_CHECK_OFFSET to PREEMPT_DISABLE_OFFSET Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 14/25] btrfs: fix use after free iterating extrefs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 06/25] skbuff: Fix skb checksum partial check. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 15/25] arm64: errata: use KBUILD_CFLAGS_MODULE for erratum #843419 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 16/25] i2c: rcar: enable RuntimePM before registering to the core Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 25/25] sched/preempt: Fix cond_resched_lock() and cond_resched_softirq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 05/25] skbuff: Fix skb checksum flag on skb pull Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 09/25] ethtool: Use kcalloc instead of kmalloc for ethtool_get_strings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  Re: [PATCH 3.14 00/25] 3.14.56-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-10-23 23:10 +0200
  Re: [PATCH 3.14 00/25] 3.14.56-stable review Guenter Roeck <linux@roeck-us.net> - 2015-10-24 04:10 +0200

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