Re: [PATCH 1/1] io_uring/sqpoll: do not put cpumask on stack

From: Jens Axboe
Date: Mon Sep 16 2024 - 06:23:19 EST


On 9/16/24 4:20 AM, Felix Moessbauer wrote:
> Putting the cpumask on the stack is deprecated for a long time (since
> 2d3854a37e8), as the masks can be big. Given that, we port-over the
> stack allocated mask to the cpumask allocation api.
>
> Fixes: f011c9cf04c0 ("io_uring/sqpoll: do not allow pinning outside of cpuset")
> Signed-off-by: Felix Moessbauer <felix.moessbauer@xxxxxxxxxxx>
> ---
> io_uring/sqpoll.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
> index 7adfcf6818ff..004740d6577e 100644
> --- a/io_uring/sqpoll.c
> +++ b/io_uring/sqpoll.c
> @@ -461,15 +461,22 @@ __cold int io_sq_offload_create(struct io_ring_ctx *ctx,
> return 0;
>
> if (p->flags & IORING_SETUP_SQ_AFF) {
> - struct cpumask allowed_mask;
> + cpumask_var_t allowed_mask;
> int cpu = p->sq_thread_cpu;
>
> ret = -EINVAL;
> + if (!alloc_cpumask_var(&allowed_mask, GFP_KERNEL)) {
> + ret = -ENOMEM;
> + goto err_sqpoll;
> + }
> if (cpu >= nr_cpu_ids || !cpu_online(cpu))
> goto err_sqpoll;

This leaks allowed_mask... Probably allocate this _after_ we've already
sanity checked the 'cpu' value itself.

--
Jens Axboe