lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-Id: <20240906134433.433083-1-felix.moessbauer@siemens.com>
Date: Fri,  6 Sep 2024 15:44:33 +0200
From: Felix Moessbauer <felix.moessbauer@...mens.com>
To: axboe@...nel.dk,
	asml.silence@...il.com
Cc: linux-kernel@...r.kernel.org,
	io-uring@...r.kernel.org,
	cgroups@...r.kernel.org,
	dqminh@...udflare.com,
	longman@...hat.com,
	adriaan.schmidt@...mens.com,
	florian.bezdeka@...mens.com,
	Felix Moessbauer <felix.moessbauer@...mens.com>,
	stable@...r.kernel.org
Subject: [PATCH 1/1] io_uring/sqpoll: inherit cpumask of creating process

The submit queue polling threads are "kernel" threads that are started
from the userland. In case the userland task is part of a cgroup with
the cpuset controller enabled, the poller should also stay within that
cpuset. This also holds, as the poller belongs to the same cgroup as
the task that started it.

With the current implementation, a process can "break out" of the
defined cpuset by creating sq pollers consuming CPU time on other CPUs,
which is especially problematic for realtime applications.

Part of this problem was fixed in a5fc1441 by dropping the
PF_NO_SETAFFINITY flag, but this only becomes effective after the first
modification of the cpuset (i.e. the pollers cpuset is correct after the
first update of the enclosing cgroups cpuset).

By inheriting the cpuset of the creating tasks, we ensure that the
poller is created with a cpumask that is a subset of the cgroups mask.
Inheriting the creators cpumask is reasonable, as other userland tasks
also inherit the mask.

Fixes: 37d1e2e3642e ("io_uring: move SQPOLL thread io-wq forked worker")
Cc: stable@...r.kernel.org # 6.1+
Signed-off-by: Felix Moessbauer <felix.moessbauer@...mens.com>
---
 io_uring/sqpoll.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
index 3b50dc9586d1..4681b2c41a96 100644
--- a/io_uring/sqpoll.c
+++ b/io_uring/sqpoll.c
@@ -289,7 +289,7 @@ static int io_sq_thread(void *data)
 	if (sqd->sq_cpu != -1) {
 		set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu));
 	} else {
-		set_cpus_allowed_ptr(current, cpu_online_mask);
+		set_cpus_allowed_ptr(current, sqd->thread->cpus_ptr);
 		sqd->sq_cpu = raw_smp_processor_id();
 	}
 
-- 
2.39.2


Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ