diff options
| author | Minchan Kim <minchan@kernel.org> | 2021-12-01 15:16:48 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-12-03 14:36:21 +0100 |
| commit | 555a0ce4558d87d5b97c4321f34b19e051c7b0c1 (patch) | |
| tree | cf04f8881289f17d5c9260e27f65540ff6e30f78 | |
| parent | 02bf607413e6110321ae75698c8ecbfa82eaafa8 (diff) | |
kernfs: prevent early freeing of root node
Marek reported the warning below.
=========================
WARNING: held lock freed!
5.16.0-rc2+ #10984 Not tainted
-------------------------
kworker/1:0/18 is freeing memory ffff00004034e200-ffff00004034e3ff,
with a lock still held there!
ffff00004034e348 (&root->kernfs_rwsem){++++}-{3:3}, at:
__kernfs_remove+0x310/0x37c
3 locks held by kworker/1:0/18:
#0: ffff000040107938 ((wq_completion)cgroup_destroy){+.+.}-{0:0}, at:
process_one_work+0x1f0/0x6f0
#1: ffff80000b55bdc0
((work_completion)(&(&css->destroy_rwork)->work)){+.+.}-{0:0}, at:
process_one_work+0x1f0/0x6f0
#2: ffff00004034e348 (&root->kernfs_rwsem){++++}-{3:3}, at:
__kernfs_remove+0x310/0x37c
stack backtrace:
CPU: 1 PID: 18 Comm: kworker/1:0 Not tainted 5.16.0-rc2+ #10984
Hardware name: Raspberry Pi 4 Model B (DT)
Workqueue: cgroup_destroy css_free_rwork_fn
Call trace:
dump_backtrace+0x0/0x1ac
show_stack+0x18/0x24
dump_stack_lvl+0x8c/0xb8
dump_stack+0x18/0x34
debug_check_no_locks_freed+0x124/0x140
kfree+0xf0/0x3a4
kernfs_put+0x1f8/0x224
__kernfs_remove+0x1b8/0x37c
kernfs_destroy_root+0x38/0x50
css_free_rwork_fn+0x288/0x3d4
process_one_work+0x288/0x6f0
worker_thread+0x74/0x470
kthread+0x188/0x194
ret_from_fork+0x10/0x20
Since kernfs moves the kernfs_rwsem lock into root, it couldn't hold
the lock when the root node is tearing down. Thus, get the refcount
of root node.
Fixes: 393c3714081a ("kernfs: switch global kernfs_rwsem lock to per-fs lock")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Link: https://lore.kernel.org/r/20211201231648.1027165-1-minchan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/kernfs/dir.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 13cae0ccce74..e6d9772ddb4c 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -961,7 +961,13 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops, */ void kernfs_destroy_root(struct kernfs_root *root) { - kernfs_remove(root->kn); /* will also free @root */ + /* + * kernfs_remove holds kernfs_rwsem from the root so the root + * shouldn't be freed during the operation. + */ + kernfs_get(root->kn); + kernfs_remove(root->kn); + kernfs_put(root->kn); /* will also free @root */ } /** |