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.
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
I am bit skeptical about the condition when btrfs_commit_transaction()
fails, can you pls be wary about it when reviewing. Thanks.
Lu/David,
As this issues isn't reproducible at my end, can you pls test this
patch on top of the patch
btrfs: fix missing superblock update in the device delete commit transaction
Thanks.
fs/btrfs/volumes.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 418843b8f8e8..344083cc811c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4464,7 +4464,10 @@ 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)
+ btrfs_end_transaction(trans);
+ else
+ ret = btrfs_commit_transaction(trans);
done:
btrfs_free_path(path);
if (ret) {
--
2.7.0
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