[PATCH v3 32/46] kmsan: disable physical page merging in biovec

[Alexander Potapenko]

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@xxxxxxxxxx>
---

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 8ccbc6e076369..95815ac559743 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))
-- 
2.36.0.rc2.479.g8af0fa9b8e-goog