Commit 84029fd0 authored Jan 04, 2020 by Shakeel Butt Committed by Linus Torvalds Jan 04, 2020

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 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@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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a69b83e1

kernel/cred.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -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);

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