[PATCH 3.16.y-ckt 31/94] btrfs: fix use after free iterating extrefs

From: Luis Henriques
Date: Fri Nov 13 2015 - 05:47:23 EST


3.16.7-ckt20 -stable review patch. If anyone has any objections, please let me know.

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

From: Chris Mason <clm@xxxxxx>

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@xxxxxx>
cc: Mark Fasheh <mfasheh@xxxxxxx>
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: Mark Fasheh <mfasheh@xxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
fs/btrfs/backref.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 54a201dac7f9..b16815417125 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -1693,7 +1693,6 @@ static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
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;
@@ -1721,9 +1720,8 @@ static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
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) {
@@ -1737,7 +1735,7 @@ static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
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);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/