[PATCH 4.14 106/191] f2fs: wait for sysfs kobject removal before freeing f2fs_sb_info

Greg Kroah-Hartman
2020-10-27T14:17:47Z

From: Jamie Iles <jamie@nuviainc.com>

[ Upstream commit ae284d87abade58c8db7760c808f311ef1ce693c ]

syzkaller found that with CONFIG_DEBUG_KOBJECT_RELEASE=y, unmounting an
f2fs filesystem could result in the following splat:

kobject: 'loop5' ((____ptrval____)): kobject_release, parent 0000000000000000 (delayed 250)
kobject: 'f2fs_xattr_entry-7:5' ((____ptrval____)): kobject_release, parent 0000000000000000 (delayed 750)
------------[ cut here ]------------
ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x98
WARNING: CPU: 0 PID: 699 at lib/debugobjects.c:485 debug_print_object+0x180/0x240
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 699 Comm: syz-executor.5 Tainted: G S 5.9.0-rc8+ #101
Hardware name: linux,dummy-virt (DT)
Call trace:
dump_backtrace+0x0/0x4d8
show_stack+0x34/0x48
dump_stack+0x174/0x1f8
panic+0x360/0x7a0
__warn+0x244/0x2ec
report_bug+0x240/0x398
bug_handler+0x50/0xc0
call_break_hook+0x160/0x1d8
brk_handler+0x30/0xc0
do_debug_exception+0x184/0x340
el1_dbg+0x48/0xb0
el1_sync_handler+0x170/0x1c8
el1_sync+0x80/0x100
debug_print_object+0x180/0x240
debug_check_no_obj_freed+0x200/0x430
slab_free_freelist_hook+0x190/0x210
kfree+0x13c/0x460
f2fs_put_super+0x624/0xa58
generic_shutdown_super+0x120/0x300
kill_block_super+0x94/0xf8
kill_f2fs_super+0x244/0x308
deactivate_locked_super+0x104/0x150
deactivate_super+0x118/0x148
cleanup_mnt+0x27c/0x3c0
__cleanup_mnt+0x28/0x38
task_work_run+0x10c/0x248
do_notify_resume+0x9d4/0x1188
work_pending+0x8/0x34c

Like the error handling for f2fs_register_sysfs(), we need to wait for
the kobject to be destroyed before returning to prevent a potential
use-after-free.

Fixes: bf9e697ecd42 ("f2fs: expose features to sysfs entry")
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <chao@kernel.org>
Signed-off-by: Jamie Iles <jamie@nuviainc.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/sysfs.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index a55919eec0351..6a13099b3c823 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -563,4 +563,5 @@ void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
}
kobject_del(&sbi->s_kobj);
kobject_put(&sbi->s_kobj);
+ wait_for_completion(&sbi->s_kobj_unregister);
}
--
2.25.1