test case btrfs/164 reported UAF..
[ 6712.084324] general protection fault: 0000 [#1] PREEMPT SMP
::
[ 6712.195423] btrfs_update_commit_device_size+0x75/0xf0 [btrfs]
[ 6712.201424] btrfs_commit_transaction+0x57d/0xa90 [btrfs]
[ 6712.206999] btrfs_rm_device+0x627/0x850 [btrfs]
[ 6712.211800] btrfs_ioctl+0x2b03/0x3120 [btrfs]
::
reason for this is that btrfs_shrink_device() adds the device resized to
the fs_devices::resized_devices after it has called the last commit
transaction.
So the list fs_devices::resized_devices is not empty when
btrfs_shrink_device() returns.
Now the parent function btrfs_rm_device() calls
btrfs_close_bdev(device);
call_rcu(&device->rcu, free_device_rcu);
and then does the commit transaction.
The commit transaction goes through the fs_devices::resized_devices
in btrfs_update_commit_device_size() and leads to UAF.
Fix this by making sure btrfs_shrink_device() calls the last needed
btrfs_commit_transaction() before the return.
Reported-by: Lu Fengqi <lufq.f...@cn.fujitsu.com>
Signed-off-by: Anand Jain <anand.j...@oracle.com>
Tested-by: Lu Fengqi <lufq.f...@cn.fujitsu.com>
---
v1->v2: cleanup the dirty and new meta block group before ending
the transaction when btrfs_update_device fails.
fs/btrfs/volumes.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index da86706123ff..f4405e430da6 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4491,7 +4491,12 @@ int btrfs_shrink_device(struct btrfs_device *device, u64
new_size)
/* Now btrfs_update_device() will change the on-disk size. */
ret = btrfs_update_device(trans, device);
- btrfs_end_transaction(trans);
+ if (ret < 0) {
+ btrfs_abort_transaction(trans, ret);
+ btrfs_end_transaction(trans);
+ } else {
+ ret = btrfs_commit_transaction(trans);
+ }
done:
btrfs_free_path(path);
if (ret) {
--
2.7.0
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