Commit cbf8d7ac authored by Felix Moessbauer's avatar Felix Moessbauer Committed by Wen Zhiwei
Browse files

io_uring/sqpoll: do not allow pinning outside of cpuset 

stable inclusion
from stable-v6.6.54
commit 358124ba2cea9fc4d6c8d40607cac4a22f62ffe4
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAZ3K2

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=358124ba2cea9fc4d6c8d40607cac4a22f62ffe4



--------------------------------

commit f011c9cf04c06f16b24f583d313d3c012e589e50 upstream.

The submit queue polling threads are userland threads that just never
exit to the userland. When creating the thread with IORING_SETUP_SQ_AFF,
the affinity of the poller thread is set to the cpu specified in
sq_thread_cpu. However, this CPU can be outside of the cpuset defined
by the cgroup cpuset controller. This violates the rules defined by the
cpuset controller and is a potential issue for realtime applications.

In b7ed6d8ffd6 we fixed the default affinity of the poller thread, in
case no explicit pinning is required by inheriting the one of the
creating task. In case of explicit pinning, the check is more
complicated, as also a cpu outside of the parent cpumask is allowed.
We implemented this by using cpuset_cpus_allowed (that has support for
cgroup cpusets) and testing if the requested cpu is in the set.

Fixes: 37d1e2e3 ("io_uring: move SQPOLL thread io-wq forked worker")
Cc: stable@vger.kernel.org # 6.1+
Signed-off-by: default avatarFelix Moessbauer <felix.moessbauer@siemens.com>
Link: https://lore.kernel.org/r/20240909150036.55921-1-felix.moessbauer@siemens.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarWen Zhiwei <wenzhiwei@kylinos.cn>
parent 25e04194

io_uring/sqpoll.c

+4 −1
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#include <linux/slab.h>

#include <linux/audit.h>

#include <linux/security.h>

#include <linux/cpuset.h>

#include <linux/io_uring.h>



#include <uapi/linux/io_uring.h>
@@ -401,10 +402,12 @@ __cold int io_sq_offload_create(struct io_ring_ctx *ctx, 
			return 0;



		if (p->flags & IORING_SETUP_SQ_AFF) {

			struct cpumask allowed_mask;

			int cpu = p->sq_thread_cpu;



			ret = -EINVAL;

			if (cpu >= nr_cpu_ids || !cpu_online(cpu))

			cpuset_cpus_allowed(current, &allowed_mask);

			if (!cpumask_test_cpu(cpu, &allowed_mask))

				goto err_sqpoll;

			sqd->sq_cpu = cpu;

		} else {