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Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH 16/16] mm/sl[au]b: check if large object is valid in __ksize() Content-Language: en-US To: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Joe Perches , Vasily Averin , Matthew WilCox , Marco Elver Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20220712133946.307181-1-42.hyeyoo@gmail.com> <20220712133946.307181-17-42.hyeyoo@gmail.com> From: Vlastimil Babka In-Reply-To: <20220712133946.307181-17-42.hyeyoo@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=N5oMKKaH; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=0YVDli1n; spf=pass (imf14.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz; 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spf=pass (imf14.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C3C971000DA X-Stat-Signature: 6gw9fb5x1ocyff6ryxpyowkpm7zd6rgr X-HE-Tag: 1659095451-509026 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: On 7/12/22 15:39, Hyeonggon Yoo wrote: > __ksize() returns size of objects allocated from slab allocator. > When invalid object is passed to __ksize(), returning zero > prevents further memory corruption and makes caller be able to > check if there is an error. > > If address of large object is not beginning of folio or size of > the folio is too small, it must be invalid. Return zero in such cases. > > Suggested-by: Vlastimil Babka > Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Reviewed-by: Vlastimil Babka If you want to change it to BUG() I won't object, no strong opinion. > --- > mm/slab_common.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 1f8db7959366..0d6cbe9d7ad0 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1013,8 +1013,12 @@ size_t __ksize(const void *object) > > folio = virt_to_folio(object); > > - if (unlikely(!folio_test_slab(folio))) > + if (unlikely(!folio_test_slab(folio))) { > + if (WARN_ON(object != folio_address(folio) || > + folio_size(folio) <= KMALLOC_MAX_CACHE_SIZE)) > + return 0; > return folio_size(folio); > + } > > return slab_ksize(folio_slab(folio)->slab_cache); > }