linux-kernel - [PATCH] epoll: account epitem and eppoll

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Message-Id: <20171003021519.23907-1-shakeelb@google.com>
Date:   Mon,  2 Oct 2017 19:15:19 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Greg Thelen <gthelen@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>
Subject: [PATCH] epoll: account epitem and eppoll_entry to kmemcg

The user space application can directly trigger the allocations
from eventpoll_epi and eventpoll_pwq slabs. A buggy or malicious
application can consume a significant amount of system memory by
triggering such allocations. Indeed we have seen in production
where a buggy application was leaking the epoll references and
causing a burst of eventpoll_epi and eventpoll_pwq slab
allocations. This patch opt-in the charging of eventpoll_epi
and eventpoll_pwq slabs.

Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
---
 fs/eventpoll.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 2fabd19cdeea..a45360444895 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2329,11 +2329,11 @@ static int __init eventpoll_init(void)
 
 	/* Allocates slab cache used to allocate "struct epitem" items */
 	epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
-			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
+			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
 
 	/* Allocates slab cache used to allocate "struct eppoll_entry" */
 	pwq_cache = kmem_cache_create("eventpoll_pwq",
-			sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL);
+		sizeof(struct eppoll_entry), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL);
 
 	return 0;
 }
-- 
2.14.2.822.g60be5d43e6-goog