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From:   Vasily Averin <vvs@virtuozzo.com>
Subject: [PATCH v5 08/16] memcg: enable accounting for pollfd and select bits
 arrays
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     cgroups@vger.kernel.org, Michal Hocko <mhocko@kernel.org>,
        Shakeel Butt <shakeelb@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Roman Gushchin <guro@fb.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
References: <CALvZod66KF-8xKB1dyY2twizDE=svE8iXT_nqvsrfWg1a92f4A@mail.gmail.com>
 <cover.1626688654.git.vvs@virtuozzo.com>
Message-ID: <4e3cb762-73b4-d4d2-487d-37a414073141@virtuozzo.com>
Date:   Mon, 19 Jul 2021 13:45:09 +0300
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User can call select/poll system calls with a large number of assigned
file descriptors and force kernel to allocate up to several pages of memory
till end of these sleeping system calls. We have here long-living
unaccounted per-task allocations.

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@virtuozzo.com>
---
 fs/select.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/select.c b/fs/select.c
index 945896d..e83e563 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -655,7 +655,7 @@ int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 			goto out_nofds;
 
 		alloc_size = 6 * size;
-		bits = kvmalloc(alloc_size, GFP_KERNEL);
+		bits = kvmalloc(alloc_size, GFP_KERNEL_ACCOUNT);
 		if (!bits)
 			goto out_nofds;
 	}
@@ -1000,7 +1000,7 @@ static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 
 		len = min(todo, POLLFD_PER_PAGE);
 		walk = walk->next = kmalloc(struct_size(walk, entries, len),
-					    GFP_KERNEL);
+					    GFP_KERNEL_ACCOUNT);
 		if (!walk) {
 			err = -ENOMEM;
 			goto out_fds;
-- 
1.8.3.1