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io_uring: fix race with canceling timeouts

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If we get -1 from hrtimer_try_to_cancel(), we know that the timer
is running. Hence leave all completion to the timeout handler. If
we don't, we can corrupt the list and miss a completion.

Fixes: 11365043e5 ("io_uring: add support for canceling timeout requests")
Reported-by: Hrvoje Zeba <zeba.hrvoje@gmail.com>
Tested-by: Hrvoje Zeba <zeba.hrvoje@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2019-10-29 12:34:10 -06:00
parent 65e19f54d2
commit 842f96124c
1 changed files with 8 additions and 12 deletions
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20
fs/io_uring.c
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@ -533,7 +533,7 @@ static void io_kill_timeout(struct io_kiocb *req)
ret = hrtimer_try_to_cancel(&req->timeout.timer);
if (ret != -1) {
atomic_inc(&req->ctx->cq_timeouts);
list_del(&req->list);
list_del_init(&req->list);
io_cqring_fill_event(req->ctx, req->user_data, 0);
__io_free_req(req);
}
@ -1957,7 +1957,6 @@ static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
struct io_ring_ctx *ctx;
struct io_kiocb *req;
unsigned long flags;
bool comp;
req = container_of(timer, struct io_kiocb, timeout.timer);
ctx = req->ctx;
@ -1968,8 +1967,7 @@ static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
* We could be racing with timeout deletion. If the list is empty,
* then timeout lookup already found it and will be handling it.
*/
comp = !list_empty(&req->list);
if (comp) {
if (!list_empty(&req->list)) {
struct io_kiocb *prev;
/*
@ -1981,17 +1979,15 @@ static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
prev = req;
list_for_each_entry_continue_reverse(prev, &ctx->timeout_list, list)
prev->sequence++;
list_del_init(&req->list);
io_cqring_fill_event(ctx, req->user_data, -ETIME);
io_commit_cqring(ctx);
}
io_cqring_fill_event(ctx, req->user_data, -ETIME);
io_commit_cqring(ctx);
spin_unlock_irqrestore(&ctx->completion_lock, flags);
if (comp) {
io_cqring_ev_posted(ctx);
io_put_req(req, NULL);
}
io_cqring_ev_posted(ctx);
io_put_req(req, NULL);
return HRTIMER_NORESTART;
}
@ -2131,9 +2127,9 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
}
req->sequence -= span;
list_add(&req->list, entry);
spin_unlock_irq(&ctx->completion_lock);
req->timeout.timer.function = io_timeout_fn;
hrtimer_start(&req->timeout.timer, timespec64_to_ktime(ts), mode);
spin_unlock_irq(&ctx->completion_lock);
return 0;
}