Re: [PATCH v2] io_uring: check for user passing 0 nr_submit

[Jeff Moyer <jmoyer@redhat.com>]

Pavel Begunkov <asml.silence@gmail.com> writes:

> io_submit_sqes() shouldn't be stepping into its main loop when there is
> nothing to submit, i.e. nr=0. Fix 0 submission queue entries checks,
> which should follow after all user input truncations.

I see two callers of io_submit_sqes, and neither of them will pass 0 for
nr.  What am I missing?

-Jeff

>
> Cc: stable@vger.kernel.org
> Fixes: 6962980947e2b ("io_uring: restructure submit sqes to_submit checks")
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>
> v2: split out of the series with extra tags, no functional changes
>
>  io_uring/io_uring.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 820ef0527666..ee04ab9bf968 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -2422,10 +2422,11 @@ int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
>  	unsigned int left;
>  	int ret;
>  
> +	entries = min(nr, entries);
>  	if (unlikely(!entries))
>  		return 0;
> -	/* make sure SQ entry isn't read before tail */
> -	ret = left = min(nr, entries);
> +
> +	ret = left = entries;
>  	io_get_task_refs(left);
>  	io_submit_state_start(&ctx->submit_state, left);