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AJvYcCVxBejWtiC6YobOb59cYU9YeJijlG1u05tHEhUw7E2/2Ypu/iDLz6RlunaMi7S4/kNu0TP690aeY/qQO5E=@vger.kernel.org X-Gm-Message-State: AOJu0Yxl/bMsGedFvLFxWmVns2hLv1KIYFaoiz1PnXS8N/doCapBR3QL KjRefvSLd1GR0Pgs+jw8uPxqkzHQLp1pko2U1sGcO/MRlAWz/HhKPMTbh9EBFA0= X-Google-Smtp-Source: AGHT+IGQSK+2IQshD7ZaHoNgSTljD0BMUROfHrfP8qhqEluFOIRh7AnMrDmor+21VIn6g7IrmClwsw== X-Received: by 2002:a05:6830:61c1:b0:718:c0d:6c02 with SMTP id 46e09a7af769-71ab30f789dmr3993968a34.2.1732114905882; Wed, 20 Nov 2024 07:01:45 -0800 (PST) Received: from [192.168.1.116] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-71a78212bdfsm3984668a34.61.2024.11.20.07.01.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Nov 2024 07:01:43 -0800 (PST) Message-ID: <7e895fd8-35c5-4cf0-bd9b-239de5153999@kernel.dk> Date: Wed, 20 Nov 2024 08:01:41 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slab: Fix too strict alignment check in create_cache() To: Geert Uytterhoeven , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Pavel Begunkov , Mike Rapoport , Christian Brauner , Guenter Roeck , Kees Cook , Jann Horn Cc: linux-mm@kvack.org, io-uring@vger.kernel.org, linux-m68k@vger.kernel.org, linux-kernel@vger.kernel.org References: <80c767a5d5927c099aea5178fbf2c897b459fa90.1732106544.git.geert@linux-m68k.org> Content-Language: en-US From: Jens Axboe In-Reply-To: <80c767a5d5927c099aea5178fbf2c897b459fa90.1732106544.git.geert@linux-m68k.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/20/24 5:49 AM, Geert Uytterhoeven wrote: > On m68k, where the minimum alignment of unsigned long is 2 bytes: > > Kernel panic - not syncing: __kmem_cache_create_args: Failed to create slab 'io_kiocb'. Error -22 > CPU: 0 UID: 0 PID: 1 Comm: swapper Not tainted 6.12.0-atari-03776-g7eaa1f99261a #1783 > Stack from 0102fe5c: > 0102fe5c 00514a2b 00514a2b ffffff00 00000001 0051f5ed 00425e78 00514a2b > 0041eb74 ffffffea 00000310 0051f5ed ffffffea ffffffea 00601f60 00000044 > 0102ff20 000e7a68 0051ab8e 004383b8 0051f5ed ffffffea 000000b8 00000007 > 01020c00 00000000 000e77f0 0041e5f0 005f67c0 0051f5ed 000000b6 0102fef4 > 00000310 0102fef4 00000000 00000016 005f676c 0060a34c 00000010 00000004 > 00000038 0000009a 01000000 000000b8 005f668e 0102e000 00001372 0102ff88 > Call Trace: [<00425e78>] dump_stack+0xc/0x10 > [<0041eb74>] panic+0xd8/0x26c > [<000e7a68>] __kmem_cache_create_args+0x278/0x2e8 > [<000e77f0>] __kmem_cache_create_args+0x0/0x2e8 > [<0041e5f0>] memset+0x0/0x8c > [<005f67c0>] io_uring_init+0x54/0xd2 > > The minimal alignment of an integral type may differ from its size, > hence is not safe to assume that an arbitrary freeptr_t (which is > basically an unsigned long) is always aligned to 4 or 8 bytes. > > As nothing seems to require the additional alignment, it is safe to fix > this by relaxing the check to the actual minimum alignment of freeptr_t. > > Fixes: aaa736b186239b7d ("io_uring: specify freeptr usage for SLAB_TYPESAFE_BY_RCU io_kiocb cache") > Fixes: d345bd2e9834e2da ("mm: add kmem_cache_create_rcu()") > Reported-by: Guenter Roeck > Closes: https://lore.kernel.org/37c588d4-2c32-4aad-a19e-642961f200d7@roeck-us.net > Signed-off-by: Geert Uytterhoeven > --- > mm/slab_common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 893d320599151845..f2f201d865c108bd 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -230,7 +230,7 @@ static struct kmem_cache *create_cache(const char *name, > if (args->use_freeptr_offset && > (args->freeptr_offset >= object_size || > !(flags & SLAB_TYPESAFE_BY_RCU) || > - !IS_ALIGNED(args->freeptr_offset, sizeof(freeptr_t)))) > + !IS_ALIGNED(args->freeptr_offset, __alignof(freeptr_t)))) > goto out; > > err = -ENOMEM; This looks much better, thanks. Reviewed-by: Jens Axboe -- Jens Axboe