[PATCH v7 0/2] mm/slab, ipc: kmem_buckets kernel-doc and msg_msg accounting fixes

[PATCH v7 0/2] mm/slab, ipc: kmem_buckets kernel-doc and msg_msg accounting fixes

[Kees Cook]

Hi!

As Vlastimil suggested[1], these are the first two patches of v6, split
out for 7.4. The rest of the skb buckets series will come back for 7.5.

2/2 now keeps SLAB_ACCOUNT on the msg_msg bucket caches and allocates
with GFP_KERNEL_ACCOUNT as well, so a msg_msg is charged with
CONFIG_SLAB_BUCKETS either way.

Thanks!

-Kees

 v7:
 - split v6's 1/8 and 2/8 out for 7.4; 3/8 to 8/8 will return for 7.5
   (Vlastimil)
 - 2/2: keep SLAB_ACCOUNT in kmem_buckets_create(), and add Cc: stable
   (Vlastimil, Andrew, Harry)
 v6: https://lore.kernel.org/all/20261006092030.got.500-kees@kernel.org/
 v5: https://lore.kernel.org/all/20261002231120.late.500-kees@kernel.org/
 v4: https://lore.kernel.org/all/20260921075811.too.775-kees@kernel.org/
 v3: https://lore.kernel.org/all/20260702170728.168755-1-pfalcato@suse.de/

[1] https://lore.kernel.org/all/be34b92e-e82c-4f69-ac9d-b045081ea418@kernel.org/

Kees Cook (2):
  mm/slab: Mark the kmem_buckets_create() context as a Context: section
  ipc, msg: Account msg_msg allocations with GFP_KERNEL_ACCOUNT again

 ipc/msgutil.c    | 3 ++-
 mm/slab_common.c | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

-- 
2.55.0

[PATCH v7 1/2] mm/slab: Mark the kmem_buckets_create() context as a Context: section

[Kees Cook]

kmem_buckets_create() had the same sentence about calling context as
kmem_cache_create(), but lacked the "Context:" prefix, so kernel-doc
rendered in the body instead of as a "context" section.

Give it the missing prefix. Additionally fix the "a interrupt" typo
__kmem_cache_create_args() had.

Fixes: b32801d1255be ("mm/slab: Introduce kmem_buckets_create() and family")
Reviewed-by: Harry Yoo (Meta) <harry@kernel.org>
Acked-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Hao Li <hao.li@linux.dev>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Signed-off-by: Kees Cook <kees@kernel.org>
---
 mm/slab_common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index b19ba1b31484..270408ce5a9d 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -311,7 +311,7 @@ __kmem_cache_alias(const char *name, unsigned int size, slab_flags_t flags,
  * &SLAB_TYPESAFE_BY_RCU - Slab page (not individual objects) freeing delayed
  * by a grace period - see the full description before using.
  *
- * Context: Cannot be called within a interrupt, but can be interrupted.
+ * Context: Cannot be called within an interrupt, but can be interrupted.
  *
  * Return: a pointer to the cache on success, NULL on failure.
  */
@@ -422,7 +422,7 @@ static struct kmem_cache *kmem_buckets_cache __ro_after_init;
  *		to/from userspace.
  * @ctor: A constructor for the objects, run when new allocations are made.
  *
- * Cannot be called within an interrupt, but can be interrupted.
+ * Context: Cannot be called within an interrupt, but can be interrupted.
  *
  * Return: a pointer to the cache on success, NULL on failure. When
  * CONFIG_SLAB_BUCKETS is not enabled, ZERO_SIZE_PTR is returned, and
-- 
2.55.0

[PATCH v7 2/2] ipc, msg: Account msg_msg allocations with GFP_KERNEL_ACCOUNT again

[Kees Cook]

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, so the
allocation is charged whichever cache serves it.

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()")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
---
 ipc/msgutil.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index e28f0cecb2ec..12663a40e9ae 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -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