diff options
| author | Filipe Manana <fdmanana@suse.com> | 2022-08-23 14:45:42 +0300 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2022-09-26 13:27:58 +0300 |
| commit | 331cd9461412e103d07595a10289de90004ac890 (patch) | |
| tree | eb9429aba3331512dec86301a4c1ca5b6d6987b9 | |
| parent | dbecac26630014d336a8e5ea67096ff18210fb9c (diff) | |
| download | linux-331cd9461412e103d07595a10289de90004ac890.tar.xz | |
btrfs: fix race between quota enable and quota rescan ioctl
When enabling quotas, at btrfs_quota_enable(), after committing the
transaction, we change fs_info->quota_root to point to the quota root we
created and set BTRFS_FS_QUOTA_ENABLED at fs_info->flags. Then we try
to start the qgroup rescan worker, first by initializing it with a call
to qgroup_rescan_init() - however if that fails we end up freeing the
quota root but we leave fs_info->quota_root still pointing to it, this
can later result in a use-after-free somewhere else.
We have previously set the flags BTRFS_FS_QUOTA_ENABLED and
BTRFS_QGROUP_STATUS_FLAG_ON, so we can only fail with -EINPROGRESS at
btrfs_quota_enable(), which is possible if someone already called the
quota rescan ioctl, and therefore started the rescan worker.
So fix this by ignoring an -EINPROGRESS and asserting we can't get any
other error.
Reported-by: Ye Bin <yebin10@huawei.com>
Link: https://lore.kernel.org/linux-btrfs/20220823015931.421355-1-yebin10@huawei.com/
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/qgroup.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index db723c0026bd..ba323dcb0a0b 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1174,6 +1174,21 @@ out_add_root: fs_info->qgroup_rescan_running = true; btrfs_queue_work(fs_info->qgroup_rescan_workers, &fs_info->qgroup_rescan_work); + } else { + /* + * We have set both BTRFS_FS_QUOTA_ENABLED and + * BTRFS_QGROUP_STATUS_FLAG_ON, so we can only fail with + * -EINPROGRESS. That can happen because someone started the + * rescan worker by calling quota rescan ioctl before we + * attempted to initialize the rescan worker. Failure due to + * quotas disabled in the meanwhile is not possible, because + * we are holding a write lock on fs_info->subvol_sem, which + * is also acquired when disabling quotas. + * Ignore such error, and any other error would need to undo + * everything we did in the transaction we just committed. + */ + ASSERT(ret == -EINPROGRESS); + ret = 0; } out_free_path: |