linux-kernel - [PATCH -next v2] io-wq: Fix memory leak in create_io

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Date:   Fri, 10 Sep 2021 15:29:10 +0800
From:   Bixuan Cui <cuibixuan@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <io-uring@...r.kernel.org>
CC:     <axboe@...nel.dk>, <asml.silence@...il.com>,
        <john.wanghui@...wei.com>
Subject: [PATCH -next v2] io-wq: Fix memory leak in create_io_worker

Kmemleak tool detected a memory leak.

====================
unreferenced object 0xffff888126fcd6c0 (size 192):
  comm "syz-executor.1", pid 11934, jiffies 4294983026 (age 15.690s)
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81632c91>] kmalloc_node include/linux/slab.h:609 [inline]
    [<ffffffff81632c91>] kzalloc_node include/linux/slab.h:732 [inline]
    [<ffffffff81632c91>] create_io_worker+0x41/0x1e0 fs/io-wq.c:739
    [<ffffffff8163311e>] io_wqe_create_worker fs/io-wq.c:267 [inline]
    [<ffffffff8163311e>] io_wqe_enqueue+0x1fe/0x330 fs/io-wq.c:866
    [<ffffffff81620b64>] io_queue_async_work+0xc4/0x200 fs/io_uring.c:1473
    [<ffffffff8162c59c>] __io_queue_sqe+0x34c/0x510 fs/io_uring.c:6933
    [<ffffffff8162c7ab>] io_req_task_submit+0x4b/0xa0 fs/io_uring.c:2233
    [<ffffffff8162cb48>] io_async_task_func+0x108/0x1c0 fs/io_uring.c:5462
    [<ffffffff816259e3>] tctx_task_work+0x1b3/0x3a0 fs/io_uring.c:2158
    [<ffffffff81269b43>] task_work_run+0x73/0xb0 kernel/task_work.c:164
    [<ffffffff812dcdd1>] tracehook_notify_signal include/linux/tracehook.h:212 [inline]
    [<ffffffff812dcdd1>] handle_signal_work kernel/entry/common.c:146 [inline]
    [<ffffffff812dcdd1>] exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
    [<ffffffff812dcdd1>] exit_to_user_mode_prepare+0x151/0x180 kernel/entry/common.c:209
    [<ffffffff843ff25d>] __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
    [<ffffffff843ff25d>] syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:302
    [<ffffffff843fa4a2>] do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
    [<ffffffff84600068>] entry_SYSCALL_64_after_hwframe+0x44/0xae
====================

If io_should_retry_thread is false in create_io_worker() and
io_queue_worker_create is false in io_workqueue_create(), free the worker.

Fixes: 3146cba99aa2 ("io-wq: make worker creation resilient against signals")
Reported-by: syzbot+65454c239241d3d647da@...kaller.appspotmail.com
Signed-off-by: Bixuan Cui <cuibixuan@...wei.com>
---
Changes in v2:
* Add free worker if io_queue_worker_create is false in io_workqueue_create();
* Add kmemleak calltrace in commit message;

 fs/io-wq.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index d80e4a735677..c24f79cf2b97 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -725,6 +725,7 @@ static void io_workqueue_create(struct work_struct *work)
 	if (!io_queue_worker_create(worker, acct, create_worker_cont)) {
 		clear_bit_unlock(0, &worker->create_state);
 		io_worker_release(worker);
+		kfree(worker);
 	}
 }
 
@@ -759,6 +760,7 @@ static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
 	if (!IS_ERR(tsk)) {
 		io_init_new_worker(wqe, worker, tsk);
 	} else if (!io_should_retry_thread(PTR_ERR(tsk))) {
+		kfree(worker);
 		goto fail;
 	} else {
 		INIT_WORK(&worker->work, io_workqueue_create);
-- 
2.17.1