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io_uring: fix race between timeout flush and removal

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commit e677edbcabee849bfdd43f1602bccbecf736a646 upstream.

io_flush_timeouts() assumes the timeout isn't in progress of triggering
or being removed/canceled, so it unconditionally removes it from the
timeout list and attempts to cancel it.

Leave it on the list and let the normal timeout cancelation take care
of it.

Cc: stable@vger.kernel.org # 5.5+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jens Axboe 2022-04-08 11:08:58 -06:00 committed by Greg Kroah-Hartman
parent f7e183b0a7
commit 2827328e64
1 changed files with 7 additions and 8 deletions
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15
fs/io_uring.c
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@ -1556,6 +1556,7 @@ static void __io_queue_deferred(struct io_ring_ctx *ctx)
static void io_flush_timeouts(struct io_ring_ctx *ctx)
{
struct io_kiocb *req, *tmp;
u32 seq;
if (list_empty(&ctx->timeout_list))
@ -1563,10 +1564,8 @@ static void io_flush_timeouts(struct io_ring_ctx *ctx)
seq = ctx->cached_cq_tail - atomic_read(&ctx->cq_timeouts);
do {
list_for_each_entry_safe(req, tmp, &ctx->timeout_list, timeout.list) {
u32 events_needed, events_got;
struct io_kiocb *req = list_first_entry(&ctx->timeout_list,
struct io_kiocb, timeout.list);
if (io_is_timeout_noseq(req))
break;
@ -1583,9 +1582,8 @@ static void io_flush_timeouts(struct io_ring_ctx *ctx)
if (events_got < events_needed)
break;
list_del_init(&req->timeout.list);
io_kill_timeout(req, 0);
} while (!list_empty(&ctx->timeout_list));
}
ctx->cq_last_tm_flush = seq;
}
@ -5639,6 +5637,7 @@ static int io_timeout_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe,
else
data->mode = HRTIMER_MODE_REL;
INIT_LIST_HEAD(&req->timeout.list);
hrtimer_init(&data->timer, CLOCK_MONOTONIC, data->mode);
return 0;
}
@ -6282,12 +6281,12 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
if (!list_empty(&req->link_list)) {
prev = list_entry(req->link_list.prev, struct io_kiocb,
link_list);
if (refcount_inc_not_zero(&prev->refs))
list_del_init(&req->link_list);
else
list_del_init(&req->link_list);
if (!refcount_inc_not_zero(&prev->refs))
prev = NULL;
}
list_del(&req->timeout.list);
spin_unlock_irqrestore(&ctx->completion_lock, flags);
if (prev) {