Re: [syzbot] memory leak in create_io_worker

[Zhang, Qiang]

________________________________________
From: syzbot <syzbot+65454c239241d3d647da@xxxxxxxxxxxxxxxxxxxxxxxxx>
Sent: Thursday, 9 September 2021 08:09
To: asml.silence@xxxxxxxxx; axboe@xxxxxxxxx; io-uring@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; syzkaller-bugs@xxxxxxxxxxxxxxxx
Subject: [syzbot] memory leak in create_io_worker

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Hello,

syzbot found the following issue on:

HEAD commit:    0bcfe68b8767 Revert "memcg: enable accounting for pollfd a..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=152ccba3300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c2f4c21cbd29de3d
dashboard link: https://syzkaller.appspot.com/bug?extid=65454c239241d3d647da
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=123d31b3300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+65454c239241d3d647da@xxxxxxxxxxxxxxxxxxxxxxxxx

2021/09/08 01:29:02 executed programs: 33
2021/09/08 01:29:08 executed programs: 42
2021/09/08 01:29:15 executed programs: 62
2021/09/08 01:29:21 executed programs: 82
BUG: 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



Hello Pavel

This looks like  io-worker create fail trigger memleak. 

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 35e7ee26f7ea..27fa0506c1a6 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -709,6 +709,7 @@ static void create_worker_cont(struct callback_head *cb)
                }
                raw_spin_unlock(&wqe->lock);
                io_worker_ref_put(wqe->wq);
+               kfree(worker);
                return;
        }

@@ -725,6 +726,7 @@ 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 +761,7 @@ 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);





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