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Date:   Tue, 18 Oct 2022 11:23:48 +0200
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Subject: Re: [PATCH AUTOSEL 5.4 10/13] kmsan: disable physical page merging in
 biovec
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To:     Eric Biggers <ebiggers@kernel.org>, Sasha Levin <sashal@kernel.org>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Alexander Potapenko <glider@google.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Christoph Hellwig <hch@lst.de>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ilya Leoshkevich <iii@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Kees Cook <keescook@chromium.org>,
        Marco Elver <elver@google.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Matthew Wilcox <willy@infradead.org>,
        "Michael S . Tsirkin" <mst@redhat.com>,
        Pekka Enberg <penberg@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Petr Mladek <pmladek@suse.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-block@vger.kernel.org
References: <20221018001102.2731930-1-sashal@kernel.org>
 <20221018001102.2731930-10-sashal@kernel.org>
 <Y03xyaUhL6gSLWYQ@sol.localdomain>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <Y03xyaUhL6gSLWYQ@sol.localdomain>
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On 10/18/22 02:22, Eric Biggers wrote:
> On Mon, Oct 17, 2022 at 08:10:59PM -0400, Sasha Levin wrote:
>> From: Alexander Potapenko <glider@google.com>
>>
>> [ Upstream commit f630a5d0ca59a6e73b61e3f82c371dc230da99ff ]
>>
>> KMSAN metadata for adjacent physical pages may not be adjacent, therefore
>> accessing such pages together may lead to metadata corruption.  We disable
>> merging pages in biovec to prevent such corruptions.
>>
>> Link: https://lkml.kernel.org/r/20220915150417.722975-28-glider@google.com
>> Signed-off-by: Alexander Potapenko <glider@google.com>
>> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
>> Cc: Alexei Starovoitov <ast@kernel.org>
>> Cc: Andrey Konovalov <andreyknvl@gmail.com>
>> Cc: Andrey Konovalov <andreyknvl@google.com>
>> Cc: Andy Lutomirski <luto@kernel.org>
>> Cc: Arnd Bergmann <arnd@arndb.de>
>> Cc: Borislav Petkov <bp@alien8.de>
>> Cc: Christoph Hellwig <hch@lst.de>
>> Cc: Christoph Lameter <cl@linux.com>
>> Cc: David Rientjes <rientjes@google.com>
>> Cc: Dmitry Vyukov <dvyukov@google.com>
>> Cc: Eric Biggers <ebiggers@google.com>
>> Cc: Eric Biggers <ebiggers@kernel.org>
>> Cc: Eric Dumazet <edumazet@google.com>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Herbert Xu <herbert@gondor.apana.org.au>
>> Cc: Ilya Leoshkevich <iii@linux.ibm.com>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Jens Axboe <axboe@kernel.dk>
>> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>> Cc: Kees Cook <keescook@chromium.org>
>> Cc: Marco Elver <elver@google.com>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Cc: Michael S. Tsirkin <mst@redhat.com>
>> Cc: Pekka Enberg <penberg@kernel.org>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Petr Mladek <pmladek@suse.com>
>> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
>> Cc: Steven Rostedt <rostedt@goodmis.org>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Vasily Gorbik <gor@linux.ibm.com>
>> Cc: Vegard Nossum <vegard.nossum@oracle.com>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>> ---
>>   block/blk.h | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/block/blk.h b/block/blk.h
>> index ee3d5664d962..3358ef4244fe 100644
>> --- a/block/blk.h
>> +++ b/block/blk.h
>> @@ -79,6 +79,13 @@ static inline bool biovec_phys_mergeable(struct request_queue *q,
>>   	phys_addr_t addr1 = page_to_phys(vec1->bv_page) + vec1->bv_offset;
>>   	phys_addr_t addr2 = page_to_phys(vec2->bv_page) + vec2->bv_offset;
>>   
>> +	/*
>> +	 * Merging adjacent physical pages may not work correctly under KMSAN
>> +	 * if their metadata pages aren't adjacent. Just disable merging.
>> +	 */
>> +	if (IS_ENABLED(CONFIG_KMSAN))
>> +		return false;
>> +
>>   	if (addr1 + vec1->bv_len != addr2)
>>   		return false;
>>   	if (xen_domain() && !xen_biovec_phys_mergeable(vec1, vec2->bv_page))
> 
> So KMSAN is being backported to 5.4?

No, AUTOSEL is drunk and should drop the random kmsan patches for random 
stable versions.

> - Eric