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author | Filipe Manana <fdmanana@suse.com> | 2018-11-19 16:20:34 +0000 |
---|---|---|
committer | David Sterba <dsterba@suse.com> | 2018-11-22 18:59:59 +0100 |
commit | 552f0329c75b3e1d7f9bb8c9e421d37403f192cd (patch) | |
tree | cb799ff55538719eea3aa5b7922d473f832f4622 /fs/btrfs/qgroup.c | |
parent | a4390aee72713d9e73f1132bcdeb17d72fbbf974 (diff) | |
download | linux-552f0329c75b3e1d7f9bb8c9e421d37403f192cd.tar.bz2 |
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.c | 3 |
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; |