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| author |   Qu Wenruo <wqu@suse.com> | 2020-08-03 14:20:11 +0800 |
|---|---|---|
| committer |   David Sterba <dsterba@suse.com> | 2020-08-10 19:51:08 +0200 |
| commit | 62ab2cc04ddc5dfab4e382ae167734fc111da5ed (patch) | |
| tree | b5bcd3c6203378f3e5aa0cb80ea4c51e40ca9f8c /fs | |
| parent | btrfs: check correct variable after allocation in btrfs_backref_iter_alloc (diff) | |
| download | wireguard-linux-62ab2cc04ddc5dfab4e382ae167734fc111da5ed.tar.xz wireguard-linux-62ab2cc04ddc5dfab4e382ae167734fc111da5ed.zip | |
btrfs: sysfs: fix NULL pointer dereference at btrfs_sysfs_del_qgroups()
[BUG]
Unmounting a btrfs filesystem with quota disabled will cause the
following NULL pointer dereference:
BTRFS info (device dm-5): has skinny extents
BUG: kernel NULL pointer dereference, address: 0000000000000018
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
CPU: 7 PID: 637 Comm: umount Not tainted 5.8.0-rc7-next-20200731-custom #76
RIP: 0010:kobject_del+0x6/0x20
Call Trace:
btrfs_sysfs_del_qgroups+0xac/0xf0 [btrfs]
btrfs_free_qgroup_config+0x63/0x70 [btrfs]
close_ctree+0x1f5/0x323 [btrfs]
btrfs_put_super+0x15/0x17 [btrfs]
generic_shutdown_super+0x72/0x110
kill_anon_super+0x18/0x30
btrfs_kill_super+0x17/0x30 [btrfs]
deactivate_locked_super+0x3b/0xa0
deactivate_super+0x40/0x50
cleanup_mnt+0x135/0x190
__cleanup_mnt+0x12/0x20
task_work_run+0x64/0xb0
exit_to_user_mode_prepare+0x18a/0x190
syscall_exit_to_user_mode+0x4f/0x270
do_syscall_64+0x45/0x50
entry_SYSCALL_64_after_hwframe+0x44/0xa9
---[ end trace 37b7adca5c1d5c5d ]---
[CAUSE]
Commit 079ad2fb4bf9 ("kobject: Avoid premature parent object freeing in
kobject_cleanup()") changed kobject_del() that it no longer accepts NULL
pointer.
Before that commit, kobject_del() and kobject_put() all accept NULL
pointers and just ignore such NULL pointers.
But that mentioned commit needs to access the parent node, killing the
old NULL pointer behavior.
Unfortunately btrfs is relying on that hidden feature thus we will
trigger such NULL pointer dereference.
[FIX]
Instead of just saving several lines, do proper fs_info->qgroups_kobj
check before calling kobject_del() and kobject_put().
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/btrfs/sysfs.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 104c80caaa74..c8df2edafd85 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -1565,9 +1565,11 @@ void btrfs_sysfs_del_qgroups(struct btrfs_fs_info *fs_info) rbtree_postorder_for_each_entry_safe(qgroup, next, &fs_info->qgroup_tree, node) btrfs_sysfs_del_one_qgroup(fs_info, qgroup); - kobject_del(fs_info->qgroups_kobj); - kobject_put(fs_info->qgroups_kobj); - fs_info->qgroups_kobj = NULL; + if (fs_info->qgroups_kobj) { + kobject_del(fs_info->qgroups_kobj); + kobject_put(fs_info->qgroups_kobj); + fs_info->qgroups_kobj = NULL; + } } /* Called when qgroups get initialized, thus there is no need for locking */ |