From: void0red <void0red@xxxxxxxxx> commit 1742e1c90c3da344f3bb9b1f1309b3f47482756a upstream. Store the error code before freeing the extent_map. Though it's reference counted structure, in that function it's the first and last allocation so this would lead to a potential use-after-free. The error can happen eg. when chunk is stored on a missing device and the degraded mount option is missing. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216721 Reported-by: eriri <1527030098@xxxxxx> Fixes: adfb69af7d8c ("btrfs: add_missing_dev() should return the actual error") CC: stable@xxxxxxxxxxxxxxx # 4.9+ Signed-off-by: void0red <void0red@xxxxxxxxx> Reviewed-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/btrfs/volumes.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -7241,8 +7241,9 @@ static int read_one_chunk(struct btrfs_k map->stripes[i].dev = handle_missing_device(fs_info, devid, uuid); if (IS_ERR(map->stripes[i].dev)) { + ret = PTR_ERR(map->stripes[i].dev); free_extent_map(em); - return PTR_ERR(map->stripes[i].dev); + return ret; } }
