[Devel] [PATCH RH7] memcg: account security cred as well to kmemcg

[Vasily Averin]

From: Shakeel Butt <shakeelb at google.com>

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 source of high overhead we found was cred->security objects, which
have a lifetime of at least the life of the process which allocated
them.

Link: http://lkml.kernel.org/r/20191205223721.40034-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb at google.com>
Acked-by: Chris Down <chris at chrisdown.name>
Reviewed-by: Roman Gushchin <guro at fb.com>
Acked-by: Michal Hocko <mhocko at suse.com>
Cc: Johannes Weiner <hannes at cmpxchg.org>
Cc: <stable at vger.kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>

(chrry-picked upstream commit 84029fd04c201a4c7e0b07ba262664900f47c6f5)
https://jira.sw.ru/browse/PSBM-108292

Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
---
 kernel/cred.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index f6bd635535fa..0984a289204b 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -209,7 +209,7 @@ 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;
@@ -267,7 +267,7 @@ 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;
@@ -620,7 +620,7 @@ 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);
-- 
2.17.1