linux-kernel - [PATCH] memcg: account security cred as well to kmemcg

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Message-Id: <20191205223721.40034-1-shakeelb@google.com>
Date:   Thu,  5 Dec 2019 14:37:21 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Roman Gushchin <guro@...com>, linux-mm@...ck.org,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>
Subject: [PATCH] memcg: account security cred as well to kmemcg

The cred_jar kmem_cache is already memcg accounted in the current
kernel but cred->security is not. Account cred->security to kmemcg.

Recently we saw high root slab usage on our production and on further
inspection, we found a buggy application leaking processes. Though that
buggy application was contained within its memcg but we observe much
more system memory overhead, couple of GiBs, during that period. This
overhead can adversely impact the isolation on the system. One of source
of high overhead, we found was cred->secuity objects.

Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
---
 kernel/cred.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index c0a4c12d38b2..9ed51b70ed80 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -223,7 +223,7 @@ struct cred *cred_alloc_blank(void)
 	new->magic = CRED_MAGIC;
 #endif
 
-	if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
+	if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
 		goto error;
 
 	return new;
@@ -282,7 +282,7 @@ struct cred *prepare_creds(void)
 	new->security = NULL;
 #endif
 
-	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
+	if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
 		goto error;
 	validate_creds(new);
 	return new;
@@ -715,7 +715,7 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
 #ifdef CONFIG_SECURITY
 	new->security = NULL;
 #endif
-	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
+	if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
 		goto error;
 
 	put_cred(old);
-- 
2.24.0.393.g34dc348eaf-goog