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b=cGjuDRH7fd9Q/vGOFT7srXE4MzTaO0zvziw1vupAjmuNfJNV1aw1OWZUFLjuLqLq/ I87VuwtS1dHs5FQ/DKdlQisdn43nyzXs9Kd4T6xzP4a1TQWy45Re6iwudrZ+5QtEFV fzz0HzS82PYt3Xg92bu5uvNyIhnz725muXUX2lfYjTmpv6xKxmB0EYSWqqZOrA1zQB 1lEKQvnQnz5DIPbu9YI7ZSuAG1Pl0hqbabAb9PpdL1iwfvHMFjz5A/s173yYvtg3Yh 4I6L0EMZ5eWiwYWI/6OsZ2o19PmZpjPcEAGi5dNXnpqJVXBO2/H1jcejotXKyWlDgu PjEnZQQ010M0w== Date: Mon, 12 Oct 2026 20:46:21 -0700 From: Kees Cook To: "Vlastimil Babka (SUSE)" Cc: Christian Brauner , Jan Kara , Andrew Morton , Roman Gushchin , Johannes Weiner , Michal Hocko , Shakeel Butt , Muchun Song , cgroups@vger.kernel.org, linux-mm@kvack.org, Pedro Falcato , Kuniyuki Iwashima , linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v6 2/8] ipc, msg: Account msg_msg allocations with GFP_KERNEL_ACCOUNT again Message-ID: <202610122044.1E1CDBF72@keescook> References: <20261006092030.got.500-kees@kernel.org> <20261006092035.166776-2-kees@kernel.org> <38befa8c-3885-44eb-813c-0ee34cd55248@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 64DE6140009 X-Stat-Signature: 5cmgjphjjcauab15aorn8drwxg7rtjr4 X-HE-Tag: 1791863182-414104 X-HE-Meta: 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 TvlxmxRE Qmx8DjBlxsx0AEz7jJd7G50SwAIYdsYbMO+krE5FtMgAZmZL+o1DWe2yCHpBJsPRQ7rGVIUaIuAYVnCtpAx+cMb+ozetkbLDCkKgG5u8qXtVnCSD+WyRSsdIDgMkLtB0VJWgqTnT2aospMKOXAWiWCqf4VDn6U3i79ISW/hxNN8pO5i0eVBZcGIx7jm/wriYGfm6HduiTUMExr1J2DxLTTPHh9m6vJwyPojjeKg5lUQL+HSj4CTL51HR4R0CkcbRBfWKUBeTaOhJh4acZVOAO9+VNPRrNejXN/HDCUuF5yzwT4L7JqUCkf1/wPwL4I8XA7fg2 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Oct 12, 2026 at 11:03:18PM +0200, Vlastimil Babka (SUSE) wrote: > 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 > > > > 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). Yeah, I'll respin with it present on the create and the alloc sides. > But for the rest we'll have to target 7.5 as it's only > a week to the 7.4 merge window now. Yeah, that's totally fine; I'm in no rush. I want to get it right, and I'm still recovering from my surprise about how GFP_KERNEL_ACCOUNT actually works. ;) -- Kees Cook