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Date:   Tue, 29 Mar 2022 14:40:03 +0200
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Subject: [PATCH v2 34/48] kmsan: disable physical page merging in biovec
From:   Alexander Potapenko <glider@google.com>
To:     glider@google.com
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        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>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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.

Signed-off-by: Alexander Potapenko <glider@google.com>
---

Link: https://linux-review.googlesource.com/id/Iece16041be5ee47904fbc98121b105e5be5fea5c
---
 block/blk.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block/blk.h b/block/blk.h
index 8bd43b3ad33d5..eb349916ac116 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -93,6 +93,13 @@ 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))
-- 
2.35.1.1021.g381101b075-goog