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Subject[PATCH 4.9 068/104] Btrfs: fix potential use-after-free for cloned bio
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Liu Bo <bo.li.liu@oracle.com>


[ Upstream commit a967efb30b3afa3d858edd6a17f544f9e9e46eea ]

KASAN reports that there is a use-after-free case of bio in btrfs_map_bio.

If we need to submit IOs to several disks at a time, the original bio
would get cloned and mapped to the destination disk, but we really should
use the original bio instead of a cloned bio to do the sanity check
because cloned bios are likely to be freed by its endio.

Reported-by: Diego <diegocg@gmail.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/volumes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6226,7 +6226,7 @@ int btrfs_map_bio(struct btrfs_root *roo
for (dev_nr = 0; dev_nr < total_devs; dev_nr++) {
dev = bbio->stripes[dev_nr].dev;
if (!dev || !dev->bdev ||
- (bio_op(bio) == REQ_OP_WRITE && !dev->writeable)) {
+ (bio_op(first_bio) == REQ_OP_WRITE && !dev->writeable)) {
bbio_error(bbio, first_bio, logical);
continue;
}

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