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io_uring: explicitly count entries for poll reqs

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If __io_queue_proc() fails to add a second poll entry, e.g. kmalloc()
failed, but it goes on with a third waitqueue, it may succeed and
overwrite the error status. Count the number of poll entries we added,
so we can set pt->error to zero at the beginning and find out when the
mentioned scenario happens.

Cc: stable@vger.kernel.org
Fixes: 18bceab101 ("io_uring: allow POLL_ADD with double poll_wait() users")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/9d6b9e561f88bcc0163623b74a76c39f712151c3.1626774457.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-07-20 10:50:43 +01:00 committed by Jens Axboe
parent 1b48773f9f
commit 68b11e8b15
1 changed files with 10 additions and 6 deletions
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16
fs/io_uring.c
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@ -4802,6 +4802,7 @@ IO_NETOP_FN(recv);
struct io_poll_table {
struct poll_table_struct pt;
struct io_kiocb *req;
int nr_entries;
int error;
};
@ -4995,11 +4996,11 @@ static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt,
struct io_kiocb *req = pt->req;
/*
* If poll->head is already set, it's because the file being polled
* uses multiple waitqueues for poll handling (eg one for read, one
* for write). Setup a separate io_poll_iocb if this happens.
* The file being polled uses multiple waitqueues for poll handling
* (e.g. one for read, one for write). Setup a separate io_poll_iocb
* if this happens.
*/
if (unlikely(poll->head)) {
if (unlikely(pt->nr_entries)) {
struct io_poll_iocb *poll_one = poll;
/* already have a 2nd entry, fail a third attempt */
@ -5027,7 +5028,7 @@ static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt,
*poll_ptr = poll;
}
pt->error = 0;
pt->nr_entries++;
poll->head = head;
if (poll->events & EPOLLEXCLUSIVE)
@ -5104,9 +5105,12 @@ static __poll_t __io_arm_poll_handler(struct io_kiocb *req,
ipt->pt._key = mask;
ipt->req = req;
ipt->error = -EINVAL;
ipt->error = 0;
ipt->nr_entries = 0;
mask = vfs_poll(req->file, &ipt->pt) & poll->events;
if (unlikely(!ipt->nr_entries) && !ipt->error)
ipt->error = -EINVAL;
spin_lock_irq(&ctx->completion_lock);
if (likely(poll->head)) {