Received-SPF: pass (google.com: domain of linux-kernel+bounces-67710-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Message-ID: <02cb04cd-0d8d-4948-b3ef-036160c52e64@suse.cz>
Date: Thu, 15 Feb 2024 22:44:02 +0100
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v3 08/35] mm: prevent slabobj_ext allocations for
 slabobj_ext and kmem_cache objects
Content-Language: en-US
To: Suren Baghdasaryan <surenb@google.com>, akpm@linux-foundation.org
Cc: kent.overstreet@linux.dev, mhocko@suse.com, hannes@cmpxchg.org,
 roman.gushchin@linux.dev, mgorman@suse.de, dave@stgolabs.net,
 willy@infradead.org, liam.howlett@oracle.com, corbet@lwn.net,
 void@manifault.com, peterz@infradead.org, juri.lelli@redhat.com,
 catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, tglx@linutronix.de,
 mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org,
 peterx@redhat.com, david@redhat.com, axboe@kernel.dk, mcgrof@kernel.org,
 masahiroy@kernel.org, nathan@kernel.org, dennis@kernel.org, tj@kernel.org,
 muchun.song@linux.dev, rppt@kernel.org, paulmck@kernel.org,
 pasha.tatashin@soleen.com, yosryahmed@google.com, yuzhao@google.com,
 dhowells@redhat.com, hughd@google.com, andreyknvl@gmail.com,
 keescook@chromium.org, ndesaulniers@google.com, vvvvvv@google.com,
 gregkh@linuxfoundation.org, ebiggers@google.com, ytcoode@gmail.com,
 vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org,
 bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com,
 penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com,
 glider@google.com, elver@google.com, dvyukov@google.com,
 shakeelb@google.com, songmuchun@bytedance.com, jbaron@akamai.com,
 rientjes@google.com, minchan@google.com, kaleshsingh@google.com,
 kernel-team@android.com, linux-doc@vger.kernel.org,
 linux-kernel@vger.kernel.org, iommu@lists.linux.dev,
 linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org,
 linux-mm@kvack.org, linux-modules@vger.kernel.org,
 kasan-dev@googlegroups.com, cgroups@vger.kernel.org
References: <20240212213922.783301-1-surenb@google.com>
 <20240212213922.783301-9-surenb@google.com>
From: Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20240212213922.783301-9-surenb@google.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit

On 2/12/24 22:38, Suren Baghdasaryan wrote:
> Use __GFP_NO_OBJ_EXT to prevent recursions when allocating slabobj_ext
> objects. Also prevent slabobj_ext allocations for kmem_cache objects.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---
>  mm/slab.h        | 6 ++++++
>  mm/slab_common.c | 2 ++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/mm/slab.h b/mm/slab.h
> index 436a126486b5..f4ff635091e4 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -589,6 +589,12 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
>  	if (!need_slab_obj_ext())
>  		return NULL;
>  
> +	if (s->flags & SLAB_NO_OBJ_EXT)
> +		return NULL;
> +
> +	if (flags & __GFP_NO_OBJ_EXT)
> +		return NULL;

Since we agreed to postpone this function, when it appears later it can have
those in.

>  	slab = virt_to_slab(p);
>  	if (!slab_obj_exts(slab) &&
>  	    WARN(alloc_slab_obj_exts(slab, s, flags, false),
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 6bfa1810da5e..83fec2dd2e2d 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -218,6 +218,8 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
>  	void *vec;
>  
>  	gfp &= ~OBJCGS_CLEAR_MASK;
> +	/* Prevent recursive extension vector allocation */
> +	gfp |= __GFP_NO_OBJ_EXT;

And this could become part of 6/35 mm: introduce __GFP_NO_OBJ_EXT ... ?

>  	vec = kcalloc_node(objects, sizeof(struct slabobj_ext), gfp,
>  			   slab_nid(slab));
>  	if (!vec)