linux-kernel - [PATCH v4 11/16] memcg: enable accounting for signals

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Message-ID: <5567ec19-cd77-01cc-b019-c48f53beb930@virtuozzo.com>
Date:   Wed, 28 Apr 2021 09:53:40 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     cgroups@...r.kernel.org, Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>
Cc:     Roman Gushchin <guro@...com>, Jens Axboe <axboe@...nel.dk>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v4 11/16] memcg: enable accounting for signals

When a user send a signal to any another processes it forces the kernel
to allocate memory for 'struct sigqueue' objects. The number of signals
is limited by RLIMIT_SIGPENDING resource limit, but even the default
settings allow each user to consume up to several megabytes of memory.
Moreover, an untrusted admin inside container can increase the limit or
create new fake users and force them to sent signals.

It makes sense to account for these allocations to restrict the host's
memory consumption from inside the memcg-limited container.

Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
---
 kernel/signal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index f271835..a7fa849 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -4639,7 +4639,7 @@ void __init signals_init(void)
 {
 	siginfo_buildtime_checks();

-	sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
+	sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC | SLAB_ACCOUNT);
 }

 #ifdef CONFIG_KGDB_KDB
-- 
1.8.3.1