On 10/12/26 19:55, Vlastimil Babka (SUSE) wrote:
> On 10/6/26 11:20, Kees Cook wrote:
>> Since commit 734bbc1c97ea7 ("ipc, msg: Use dedicated slab buckets for
>> alloc_msg()"), alloc_msg() allocates with GFP_KERNEL, and a msg_msg is
>> accounted only through SLAB_ACCOUNT on its bucket caches. With
>> CONFIG_SLAB_BUCKETS=n, kmem_buckets_create() creates no caches and
>> kmem_buckets_alloc() is a GFP_KERNEL kmalloc() from the general caches,
>> which do not account it; the same happens when kmem_buckets_create()
>> fails. Either way, the allocation is not charged to the sender's memory
>> cgroup.
>>
>> Allocate with GFP_KERNEL_ACCOUNT again, as before that commit. Memcg
>> charges such an allocation in whichever cache serves it, so drop the
>> SLAB_ACCOUNT, which no longer adds anything.
>>
>> Build tested ARCH=x86_64 defconfig with GCC 16.2.0, with
>> CONFIG_SLAB_BUCKETS as y and n.
>>
>> Fixes: 734bbc1c97ea7 ("ipc, msg: Use dedicated slab buckets for alloc_msg()")
>> Assisted-by: LLM
>> Signed-off-by: Kees Cook <[email protected]>
>
> Could we, for the purposes of a backportable fix, just have both
> SLAB_ACCOUNT and GFP_KERNEL_ACCOUNT in place? That should do the right thing
> regardless of CONFIG_SLAB_BUCKETS state, no?
BTW we're thinking to add 1+2 (once this part is clarified) for 7.4 (with
stable@ for patch 2). But for the rest we'll have to target 7.5 as it's only
a week to the 7.4 merge window now.
