Re: [PATCH] memcg: enable accounting in keyctl subsys

[Vasily Averin <vasily.averin@linux.dev>]

On 7/19/21 11:17, Yutian Yang wrote:
> This patch enables accounting for key objects and auth record objects.
> Allocation of the objects are triggerable by syscalls from userspace.
> 
> We have written a PoC to show that the missing-charging objects lead to
> breaking memcg limits. The PoC program takes around 2.2GB unaccounted
> memory, while it is charged for only 24MB memory usage. We evaluate the
> PoC on QEMU x86_64 v5.2.90 + Linux kernel v5.10.19 + Debian buster. All
> the limitations including ulimits and sysctl variables are set as default.
> Specifically, we set kernel.keys.maxbytes = 20000 and 
> kernel.keys.maxkeys = 200.
> 
> /*------------------------- POC code ----------------------------*/
[skipped]
> /*-------------------------- end --------------------------------*/

I experimented with "keyctl request2 user debug: X:Y Z" inside the container
and found that the problem is still relevant and the proposed patch solves it
correctly.

I didn't find any complaints about this patch, could someone explain why
it wasn't applied? If no one objects, I'd like to push it.

> Signed-off-by: Yutian Yang <nglaive@gmail.com>
Reviewed-by: Vasily Averin <vvs@openvz.org>

Thank you,
	Vasily Averin

PS. Should I perhaps resend it?

> ---
>  security/keys/key.c              | 4 ++--
>  security/keys/request_key_auth.c | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/security/keys/key.c b/security/keys/key.c
> index e282c6179..925d85c2e 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -279,7 +279,7 @@ struct key *key_alloc(struct key_type *type, const char *desc,
>  		goto no_memory_2;
>  
>  	key->index_key.desc_len = desclen;
> -	key->index_key.description = kmemdup(desc, desclen + 1, GFP_KERNEL);
> +	key->index_key.description = kmemdup(desc, desclen + 1, GFP_KERNEL_ACCOUNT);
>  	if (!key->index_key.description)
>  		goto no_memory_3;
>  	key->index_key.type = type;
> @@ -1198,7 +1198,7 @@ void __init key_init(void)
>  {
>  	/* allocate a slab in which we can store keys */
>  	key_jar = kmem_cache_create("key_jar", sizeof(struct key),
> -			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
> +			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
>  
>  	/* add the special key types */
>  	list_add_tail(&key_type_keyring.link, &key_types_list);
> diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
> index 41e973500..ed50a100a 100644
> --- a/security/keys/request_key_auth.c
> +++ b/security/keys/request_key_auth.c
> @@ -171,10 +171,10 @@ struct key *request_key_auth_new(struct key *target, const char *op,
>  	kenter("%d,", target->serial);
>  
>  	/* allocate a auth record */
> -	rka = kzalloc(sizeof(*rka), GFP_KERNEL);
> +	rka = kzalloc(sizeof(*rka), GFP_KERNEL_ACCOUNT);
>  	if (!rka)
>  		goto error;
> -	rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
> +	rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL_ACCOUNT);
>  	if (!rka->callout_info)
>  		goto error_free_rka;
>  	rka->callout_len = callout_len;