From: Shakeel Butt shakeelb@google.com Subject: 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, 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@google.com Acked-by: Chris Down chris@chrisdown.name Reviewed-by: Roman Gushchin guro@fb.com Acked-by: Michal Hocko mhocko@suse.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

kernel/cred.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/kernel/cred.c~memcg-account-security-cred-as-well-to-kmemcg +++ a/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 #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); _