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From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>,
	io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/3] io_uring: fix current->mm NULL dereference on exit
Date: Wed, 24 Jun 2020 19:50:08 +0300
Message-ID: <c57f2702db6a13acc194b20a34bdef06eafcc00f.1593016907.git.asml.silence@gmail.com> (raw)
In-Reply-To: <cover.1593016907.git.asml.silence@gmail.com>

Don't reissue requests from io_iopoll_reap_events(), the task may not
have mm, which ends up with NULL. It's better to kill everything off on
exit anyway.

[  677.734670] RIP: 0010:io_iopoll_complete+0x27e/0x630
...
[  677.734679] Call Trace:
[  677.734695]  ? __send_signal+0x1f2/0x420
[  677.734698]  ? _raw_spin_unlock_irqrestore+0x24/0x40
[  677.734699]  ? send_signal+0xf5/0x140
[  677.734700]  io_iopoll_getevents+0x12f/0x1a0
[  677.734702]  io_iopoll_reap_events.part.0+0x5e/0xa0
[  677.734703]  io_ring_ctx_wait_and_kill+0x132/0x1c0
[  677.734704]  io_uring_release+0x20/0x30
[  677.734706]  __fput+0xcd/0x230
[  677.734707]  ____fput+0xe/0x10
[  677.734709]  task_work_run+0x67/0xa0
[  677.734710]  do_exit+0x35d/0xb70
[  677.734712]  do_group_exit+0x43/0xa0
[  677.734713]  get_signal+0x140/0x900
[  677.734715]  do_signal+0x37/0x780
[  677.734717]  ? enqueue_hrtimer+0x41/0xb0
[  677.734718]  ? recalibrate_cpu_khz+0x10/0x10
[  677.734720]  ? ktime_get+0x3e/0xa0
[  677.734721]  ? lapic_next_deadline+0x26/0x30
[  677.734723]  ? tick_program_event+0x4d/0x90
[  677.734724]  ? __hrtimer_get_next_event+0x4d/0x80
[  677.734726]  __prepare_exit_to_usermode+0x126/0x1c0
[  677.734741]  prepare_exit_to_usermode+0x9/0x40
[  677.734742]  idtentry_exit_cond_rcu+0x4c/0x60
[  677.734743]  sysvec_reschedule_ipi+0x92/0x160
[  677.734744]  ? asm_sysvec_reschedule_ipi+0xa/0x20
[  677.734745]  asm_sysvec_reschedule_ipi+0x12/0x20

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index fb88a537f471..578ec2e39712 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -884,6 +884,7 @@ enum io_mem_account {
 	ACCT_PINNED,
 };
 
+static void io_complete_rw_common(struct kiocb *kiocb, long res);
 static void io_wq_submit_work(struct io_wq_work **workptr);
 static void io_cqring_fill_event(struct io_kiocb *req, long res);
 static void io_put_req(struct io_kiocb *req);
@@ -1756,6 +1757,14 @@ static void io_iopoll_queue(struct list_head *again)
 	do {
 		req = list_first_entry(again, struct io_kiocb, list);
 		list_del(&req->list);
+
+		/* shouldn't happen unless io_uring is dying, cancel reqs */
+		if (unlikely(!current->mm)) {
+			io_complete_rw_common(&req->rw.kiocb, -EAGAIN);
+			io_put_req(req);
+			continue;
+		}
+
 		refcount_inc(&req->refs);
 		io_queue_async_work(req);
 	} while (!list_empty(again));
-- 
2.24.0


  parent reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-24 16:50 [PATCH 0/3] iopoll fixes Pavel Begunkov
2020-06-24 16:50 ` [PATCH 1/3] io_uring: fix hanging iopoll in case of -EAGAIN Pavel Begunkov
2020-06-24 16:50 ` Pavel Begunkov [this message]
2020-06-24 16:50 ` [PATCH 3/3] io_uring: fix NULL-mm for linked reqs Pavel Begunkov
2020-06-24 17:03 ` [PATCH 0/3] iopoll fixes Pavel Begunkov
2020-06-24 19:46   ` Jens Axboe

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