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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732184355; bh=vdU01yydMwwx3sSdNOgVdvAm97pz89kQ5OB0TAdlmVI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WqOtcATb1VkKmyUI/NcRWkuA09JLY/gsuhqTD+gzFS/qKpmoOPMzMk0ePxX4ocACb 4EB2TRDNyFEsdXY/NDfvGyD/DDcn+EWCl0wSIVE237WWygYuKiQmzyjvaAdawtPcnW GIXmpkzJ/DAw+y1awNeD3VlflRD6cofwoz7W1h1+UyRUcTCG8lU0j7Tle69F7M/9f0 6BprUazlD8s8yrLdQo3ENUYufgH+duQqZkYYO+/J1Md3k5fPj0JJTU42PR2X4Bt23u M0pR0eGQLP+bRB/bTXbueKJPYPptDJ1eT1a9lN0cWG8VG8GFCFIGs1UNwyZYIYYF1Q wFsfNy8pTVlhw== Date: Thu, 21 Nov 2024 11:19:07 +0100 From: Christian Brauner To: Geert Uytterhoeven Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Jens Axboe , Pavel Begunkov , Mike@rox.of.borg, Rapoport@rox.of.borg, Guenter Roeck , Kees Cook , Jann Horn , linux-mm@kvack.org, io-uring@vger.kernel.org, linux-m68k@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] slab: Fix too strict alignment check in create_cache() Message-ID: <20241121-zwietracht-klugheit-4acf0bb07f2b@brauner> References: <80c767a5d5927c099aea5178fbf2c897b459fa90.1732106544.git.geert@linux-m68k.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <80c767a5d5927c099aea5178fbf2c897b459fa90.1732106544.git.geert@linux-m68k.org> X-Rspamd-Queue-Id: 6900F1C0010 X-Stat-Signature: qwyjh77jpagpj6o7ewimiw53amhfjf6k X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1732184290-78402 X-HE-Meta: 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 mzC8ZvcC 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Nov 20, 2024 at 01:46:21PM +0100, 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 > --- Looks good to me, Reviewed-by: Christian Brauner