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Tue, 30 Jul 2024 10:00:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id xHmFEKK5qGYCHgAAD6G6ig (envelope-from ); Tue, 30 Jul 2024 10:00:02 +0000 Message-ID: <0d6e8252-de39-4414-b4e7-b6c22a427b0d@suse.cz> Date: Tue, 30 Jul 2024 12:01:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm,slub: do not call do_slab_free for kfence object To: Chris Mason , Rik van Riel Cc: Pekka Enberg , Christoph Lameter , Andrew Morton , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , David Rientjes , kasan-dev , Jann Horn References: <20240729141928.4545a093@imladris.surriel.com> <044edc48-f597-46dd-8dc8-524697e50848@meta.com> From: Vlastimil Babka Content-Language: en-US In-Reply-To: <044edc48-f597-46dd-8dc8-524697e50848@meta.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: 43C2540029 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: x9sqob8za43w9obffafe885wgywdp7co X-HE-Tag: 1722333604-226376 X-HE-Meta: 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 DxLc+D3i 7gmaKsKKm5Z/cgxC22fHHRNqtvjZHwPnDWQOztu33ZGvWGF0ucMrae3KHtk9siIa/cVeIKcRHmwMqqzMIwNXifOBApZsjCgJaZrhjjwCIOzNxeleuwvhBf54tkdXrHCRvf+vjScqjoUscwWbv93mK27CIftT4ojoWQ9YvSzw440ulE2l+mTAd/ikzGNgNMUrZhDIJT2d04ThVICgXpDxvf0NaD/e6w6PHOYUtYfrqAJWcfnESifA8h/0XQ3rW5piqukwQk3PgOX8r+q4mkSrIxxB4msGOUm/7zPSj1Hb0kqk13LGABE/4Noy8K5tWVG5/2qMBKybcb7KOjJZb56LHBfXcysXdwcj5pxKXSC8XavGjKelbBwY1F8VJYjaDTzNRlxy+O6tenHVuDnUBhWgBOPWjcIZUuxfCv8S9U6oOZHRJH5V1TW7CBTDnFZsbatqPc4n/qvJ9x2gUOcxSZsabjo+mA9K1dTptEhO0RfJe248zIIk= 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 7/29/24 8:46 PM, Chris Mason wrote: > > > On 7/29/24 2:19 PM, Rik van Riel wrote: >> In 782f8906f805 the freeing of kfence objects was moved from deep >> inside do_free_slab to the wrapper functions outside. This is a nice >> change, but unfortunately it missed one spot in __kmem_cache_free_bulk. >> >> This results in a crash like this: >> >> BUG skbuff_head_cache (Tainted: G S B E ): Padding overwritten. 0xffff88907fea0f00-0xffff88907fea0fff @offset=3840 >> >> slab_err (mm/slub.c:1129) >> free_to_partial_list (mm/slub.c:? mm/slub.c:4036) >> slab_pad_check (mm/slub.c:864 mm/slub.c:1290) >> check_slab (mm/slub.c:?) >> free_to_partial_list (mm/slub.c:3171 mm/slub.c:4036) >> kmem_cache_alloc_bulk (mm/slub.c:? mm/slub.c:4495 mm/slub.c:4586 mm/slub.c:4635) >> napi_build_skb (net/core/skbuff.c:348 net/core/skbuff.c:527 net/core/skbuff.c:549) >> >> All the other callers to do_free_slab appear to be ok. changed do_free_slab to do_slab_free in two places. >> >> Add a kfence_free check in __kmem_cache_free_bulk to avoid the crash. >> >> Reported-by: Chris Mason >> Fixes: 782f8906f805 ("mm/slub: free KFENCE objects in slab_free_hook()") >> Cc: stable@kernel.org >> Signed-off-by: Rik van Riel > > We found this after bisecting a slab corruption down to the kfence > patch, and with this patch applied we're no longer falling over. So > thanks Rik! Indeed thanks and sorry for the trouble! Given that __kmem_cache_free_bulk is currently only used to unwind a kmem_cache_bulk_alloc() that runs out of memory in the middle of the operation, I'm surprised you saw this happen reliably enough to bisect it. Added to slab/for-6.11-rc1/fixes > -chris