[PATCH net-next v6 2/8] ipc, msg: Account msg_msg allocations with GFP_KERNEL_ACCOUNT again

[Kees Cook <kees@kernel.org>]

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 <kees@kernel.org>
---
 ipc/msgutil.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index e28f0cecb2ec..1ba8e59cb255 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -43,7 +43,7 @@ static kmem_buckets *msg_buckets __ro_after_init;
 
 static int __init init_msg_buckets(void)
 {
-	msg_buckets = kmem_buckets_create("msg_msg", SLAB_ACCOUNT,
+	msg_buckets = kmem_buckets_create("msg_msg", 0,
 					  sizeof(struct msg_msg),
 					  DATALEN_MSG, NULL);
 
@@ -58,7 +58,8 @@ static struct msg_msg *alloc_msg(size_t len)
 	size_t alen;
 
 	alen = min(len, DATALEN_MSG);
-	msg = kmem_buckets_alloc(msg_buckets, sizeof(*msg) + alen, GFP_KERNEL);
+	msg = kmem_buckets_alloc(msg_buckets, sizeof(*msg) + alen,
+				 GFP_KERNEL_ACCOUNT);
 	if (msg == NULL)
 		return NULL;
 
-- 
2.55.0