From: Anand Jain <anand.j...@oracle.com> %fs_devices can be free-ed by btrfs_free_stale_devices() when the close_fs_devices() drops fs_devices::opened to zero, but close_fs_devices tries to access the %fs_devices again without the device_list_mutex.
Fix this by bringing the %fs_devices access with in the device_list_mutex. Stack trace as below. WARNING: CPU: 1 PID: 4499 at fs/btrfs/volumes.c:1071 close_fs_devices+0xbc7/0xfa0 fs/btrfs/volumes.c:1071 Kernel panic - not syncing: panic_on_warn set ... :: RIP: 0010:close_fs_devices+0xbc7/0xfa0 fs/btrfs/volumes.c:1071 :: btrfs_close_devices+0x29/0x150 fs/btrfs/volumes.c:1085 open_ctree+0x589/0x7898 fs/btrfs/disk-io.c:3358 btrfs_fill_super fs/btrfs/super.c:1202 [inline] btrfs_mount_root+0x16df/0x1e70 fs/btrfs/super.c:1593 mount_fs+0xae/0x328 fs/super.c:1277 vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037 vfs_kern_mount+0x40/0x60 fs/namespace.c:1027 btrfs_mount+0x4a1/0x213e fs/btrfs/super.c:1661 mount_fs+0xae/0x328 fs/super.c:1277 Reported-by: syzbot+ceb2606025ec1cc34...@syzkaller.appspotmail.com Signed-off-by: Anand Jain <anand.j...@oracle.com> --- v1->v2: Commit log update. Satisfy checkpatch.pl. Remove HEAD.. fs/btrfs/volumes.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 870c9f69a6a4..8450bcfed4cb 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1062,13 +1062,13 @@ static int close_fs_devices(struct btrfs_fs_devices *fs_devices) list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) { btrfs_close_one_device(device); } - mutex_unlock(&fs_devices->device_list_mutex); - WARN_ON(fs_devices->open_devices); WARN_ON(fs_devices->rw_devices); fs_devices->opened = 0; fs_devices->seeding = 0; + mutex_unlock(&fs_devices->device_list_mutex); + return 0; } -- 2.7.0 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html