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Mon, 24 Jun 2024 07:34:38 +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 qB+lKo4heWb8fgAAD6G6ig (envelope-from ); Mon, 24 Jun 2024 07:34:38 +0000 Message-ID: <56e9564d-0b01-484c-a491-acd6d15e0b26@suse.cz> Date: Mon, 24 Jun 2024 09:34:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 18/38] mm: slub: Disable KMSAN when checking the padding bytes Content-Language: en-US To: Ilya Leoshkevich , Alexander Gordeev , Alexander Potapenko , Andrew Morton , Christoph Lameter , David Rientjes , Heiko Carstens , Joonsoo Kim , Marco Elver , Masami Hiramatsu , Pekka Enberg , Steven Rostedt , Vasily Gorbik Cc: Christian Borntraeger , Dmitry Vyukov , Hyeonggon Yoo <42.hyeyoo@gmail.com>, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Mark Rutland , Roman Gushchin , Sven Schnelle References: <20240621113706.315500-1-iii@linux.ibm.com> <20240621113706.315500-19-iii@linux.ibm.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 8B41A40004 X-Stat-Signature: gcppzd7gp4fy6p5t4zde96syd8x3jwsd X-Rspam-User: X-HE-Tag: 1719214480-927735 X-HE-Meta: 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 Lnu24U16 sS6iJwvtj/mPzBAg+yP3W5N5g2RfGGuvXOyEp6mzKGEaJgJQ/Y4tNXqurKWD1zYKV52rEPP+ZG65DDFnzOnnZm6IRZSW28l6sSLUWH4taTCdpILCZCWjKeeWBElNSsi14b5fhxLT+hk5FqIbUqWR2ID7U+20OToadZZDZX4pVIaF2JSHe9aC7fr8lC9WGTD2GWYNkOeZFsX9dE3WwmKZykVzPbhNNLVAXYoK7x/8KXzLHGow8WZjHv/oQOdiuIYxE6Dbo6mEh+iDZOXksxGiuVP98pBtwM4GR/trB3xVPfwLriAojPeT8IvkxUxS6vbu5CCKmFYIZX4iLqoEgDB+/CnfZaYD9wqfbvWW4Qkr5fteDZ0QFZ0csF2VHQdTMJhE7OpdZ 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 6/21/24 1:35 PM, Ilya Leoshkevich wrote: > Even though the KMSAN warnings generated by memchr_inv() are suppressed > by metadata_access_enable(), its return value may still be poisoned. > > The reason is that the last iteration of memchr_inv() returns > `*start != value ? start : NULL`, where *start is poisoned. Because of > this, somewhat counterintuitively, the shadow value computed by > visitSelectInst() is equal to `(uintptr_t)start`. > > One possibility to fix this, since the intention behind guarding > memchr_inv() behind metadata_access_enable() is to touch poisoned > metadata without triggering KMSAN, is to unpoison its return value. > However, this approach is too fragile. So simply disable the KMSAN > checks in the respective functions. > > Reviewed-by: Alexander Potapenko > Signed-off-by: Ilya Leoshkevich Acked-by: Vlastimil Babka > --- > mm/slub.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index b050e528112c..fcd68fcea4ab 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1176,9 +1176,16 @@ static void restore_bytes(struct kmem_cache *s, char *message, u8 data, > memset(from, data, to - from); > } > > -static int check_bytes_and_report(struct kmem_cache *s, struct slab *slab, > - u8 *object, char *what, > - u8 *start, unsigned int value, unsigned int bytes) > +#ifdef CONFIG_KMSAN > +#define pad_check_attributes noinline __no_kmsan_checks > +#else > +#define pad_check_attributes > +#endif > + > +static pad_check_attributes int > +check_bytes_and_report(struct kmem_cache *s, struct slab *slab, > + u8 *object, char *what, > + u8 *start, unsigned int value, unsigned int bytes) > { > u8 *fault; > u8 *end; > @@ -1270,7 +1277,8 @@ static int check_pad_bytes(struct kmem_cache *s, struct slab *slab, u8 *p) > } > > /* Check the pad bytes at the end of a slab page */ > -static void slab_pad_check(struct kmem_cache *s, struct slab *slab) > +static pad_check_attributes void > +slab_pad_check(struct kmem_cache *s, struct slab *slab) > { > u8 *start; > u8 *fault;