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/9d6b9e561f88bcc0163623b74a76c39f712151c3.162677445... 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 @@ -4916,6 +4916,7 @@ static int io_connect(struct io_kiocb *r struct io_poll_table { struct poll_table_struct pt; struct io_kiocb *req; + int nr_entries; int error; };
@@ -5098,11 +5099,11 @@ 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 */ @@ -5124,7 +5125,7 @@ static void __io_queue_proc(struct io_po *poll_ptr = poll; }
- pt->error = 0; + pt->nr_entries++; poll->head = head;
if (poll->events & EPOLLEXCLUSIVE) @@ -5210,9 +5211,12 @@ 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)) {