| From 68b11e8b1562986c134764433af64e97d30c9fc0 Mon Sep 17 00:00:00 2001 |
| From: Pavel Begunkov <asml.silence@gmail.com> |
| Date: Tue, 20 Jul 2021 10:50:43 +0100 |
| Subject: io_uring: explicitly count entries for poll reqs |
| |
| From: Pavel Begunkov <asml.silence@gmail.com> |
| |
| commit 68b11e8b1562986c134764433af64e97d30c9fc0 upstream. |
| |
| 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: 18bceab101add ("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> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| fs/io_uring.c | 16 ++++++++++------ |
| 1 file changed, 10 insertions(+), 6 deletions(-) |
| |
| --- a/fs/io_uring.c |
| +++ b/fs/io_uring.c |
| @@ -4805,6 +4805,7 @@ IO_NETOP_FN(recv); |
| struct io_poll_table { |
| struct poll_table_struct pt; |
| struct io_kiocb *req; |
| + int nr_entries; |
| int error; |
| }; |
| |
| @@ -5002,11 +5003,11 @@ static void __io_queue_proc(struct io_po |
| 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 */ |
| @@ -5034,7 +5035,7 @@ static void __io_queue_proc(struct io_po |
| *poll_ptr = poll; |
| } |
| |
| - pt->error = 0; |
| + pt->nr_entries++; |
| poll->head = head; |
| |
| if (poll->events & EPOLLEXCLUSIVE) |
| @@ -5112,9 +5113,12 @@ static __poll_t __io_arm_poll_handler(st |
| |
| 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)) { |