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Subject[PATCH 5.10 11/54] io_uring: fix cancellation taking mutex while TASK_UNINTERRUPTIBLE
Date
From: Pavel Begunkov <asml.silence@gmail.com>

[ Upstream commit ca70f00bed6cb255b7a9b91aa18a2717c9217f70 ]

do not call blocking ops when !TASK_RUNNING; state=2 set at
[<00000000ced9dbfc>] prepare_to_wait+0x1f4/0x3b0
kernel/sched/wait.c:262
WARNING: CPU: 1 PID: 19888 at kernel/sched/core.c:7853
__might_sleep+0xed/0x100 kernel/sched/core.c:7848
RIP: 0010:__might_sleep+0xed/0x100 kernel/sched/core.c:7848
Call Trace:
__mutex_lock_common+0xc4/0x2ef0 kernel/locking/mutex.c:935
__mutex_lock kernel/locking/mutex.c:1103 [inline]
mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1118
io_wq_submit_work+0x39a/0x720 fs/io_uring.c:6411
io_run_cancel fs/io-wq.c:856 [inline]
io_wqe_cancel_pending_work fs/io-wq.c:990 [inline]
io_wq_cancel_cb+0x614/0xcb0 fs/io-wq.c:1027
io_uring_cancel_files fs/io_uring.c:8874 [inline]
io_uring_cancel_task_requests fs/io_uring.c:8952 [inline]
__io_uring_files_cancel+0x115d/0x19e0 fs/io_uring.c:9038
io_uring_files_cancel include/linux/io_uring.h:51 [inline]
do_exit+0x2e6/0x2490 kernel/exit.c:780
do_group_exit+0x168/0x2d0 kernel/exit.c:922
get_signal+0x16b5/0x2030 kernel/signal.c:2770
arch_do_signal_or_restart+0x8e/0x6a0 arch/x86/kernel/signal.c:811
handle_signal_work kernel/entry/common.c:147 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0xac/0x1e0 kernel/entry/common.c:201
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x48/0x190 kernel/entry/common.c:302
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Rewrite io_uring_cancel_files() to mimic __io_uring_task_cancel()'s
counting scheme, so it does all the heavy work before setting
TASK_UNINTERRUPTIBLE.

Cc: stable@vger.kernel.org # 5.9+
Reported-by: syzbot+f655445043a26a7cfab8@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: fix inverted task check]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/io_uring.c | 39 ++++++++++++++++++++++-----------------
1 file changed, 22 insertions(+), 17 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8586,30 +8586,31 @@ static void io_cancel_defer_files(struct
}
}

+static int io_uring_count_inflight(struct io_ring_ctx *ctx,
+ struct task_struct *task,
+ struct files_struct *files)
+{
+ struct io_kiocb *req;
+ int cnt = 0;
+
+ spin_lock_irq(&ctx->inflight_lock);
+ list_for_each_entry(req, &ctx->inflight_list, inflight_entry)
+ cnt += io_match_task(req, task, files);
+ spin_unlock_irq(&ctx->inflight_lock);
+ return cnt;
+}
+
static void io_uring_cancel_files(struct io_ring_ctx *ctx,
struct task_struct *task,
struct files_struct *files)
{
while (!list_empty_careful(&ctx->inflight_list)) {
struct io_task_cancel cancel = { .task = task, .files = files };
- struct io_kiocb *req;
DEFINE_WAIT(wait);
- bool found = false;
+ int inflight;

- spin_lock_irq(&ctx->inflight_lock);
- list_for_each_entry(req, &ctx->inflight_list, inflight_entry) {
- if (!io_match_task(req, task, files))
- continue;
- found = true;
- break;
- }
- if (found)
- prepare_to_wait(&task->io_uring->wait, &wait,
- TASK_UNINTERRUPTIBLE);
- spin_unlock_irq(&ctx->inflight_lock);
-
- /* We need to keep going until we don't find a matching req */
- if (!found)
+ inflight = io_uring_count_inflight(ctx, task, files);
+ if (!inflight)
break;

io_wq_cancel_cb(ctx->io_wq, io_cancel_task_cb, &cancel, true);
@@ -8617,7 +8618,11 @@ static void io_uring_cancel_files(struct
io_kill_timeouts(ctx, task, files);
/* cancellations _may_ trigger task work */
io_run_task_work();
- schedule();
+
+ prepare_to_wait(&task->io_uring->wait, &wait,
+ TASK_UNINTERRUPTIBLE);
+ if (inflight == io_uring_count_inflight(ctx, task, files))
+ schedule();
finish_wait(&task->io_uring->wait, &wait);
}
}

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