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authorFilipe Manana <fdmanana@suse.com>2018-11-19 16:20:34 +0000
committerDavid Sterba <dsterba@suse.com>2018-11-22 18:59:59 +0100
commit552f0329c75b3e1d7f9bb8c9e421d37403f192cd (patch)
treecb799ff55538719eea3aa5b7922d473f832f4622 /fs/btrfs/qgroup.c
parenta4390aee72713d9e73f1132bcdeb17d72fbbf974 (diff)
Btrfs: fix race between enabling quotas and subvolume creation
We have a race between enabling quotas end subvolume creation that cause subvolume creation to fail with -EINVAL, and the following diagram shows how it happens: CPU 0 CPU 1 btrfs_ioctl() btrfs_ioctl_quota_ctl() btrfs_quota_enable() mutex_lock(fs_info->qgroup_ioctl_lock) btrfs_ioctl() create_subvol() btrfs_qgroup_inherit() -> save fs_info->quota_root into quota_root -> stores a NULL value -> tries to lock the mutex qgroup_ioctl_lock -> blocks waiting for the task at CPU0 -> sets BTRFS_FS_QUOTA_ENABLED in fs_info -> sets quota_root in fs_info->quota_root (non-NULL value) mutex_unlock(fs_info->qgroup_ioctl_lock) -> checks quota enabled flag is set -> returns -EINVAL because fs_info->quota_root was NULL before it acquired the mutex qgroup_ioctl_lock -> ioctl returns -EINVAL Returning -EINVAL to user space will be confusing if all the arguments passed to the subvolume creation ioctl were valid. Fix it by grabbing the value from fs_info->quota_root after acquiring the mutex. CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/qgroup.c')
-rw-r--r--fs/btrfs/qgroup.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 45868fd76209..f70825af6438 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2659,7 +2659,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
int i;
u64 *i_qgroups;
struct btrfs_fs_info *fs_info = trans->fs_info;
- struct btrfs_root *quota_root = fs_info->quota_root;
+ struct btrfs_root *quota_root;
struct btrfs_qgroup *srcgroup;
struct btrfs_qgroup *dstgroup;
u32 level_size = 0;
@@ -2669,6 +2669,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
goto out;
+ quota_root = fs_info->quota_root;
if (!quota_root) {
ret = -EINVAL;
goto out;