[PATCH 6.6.y] dm-integrity: require stable writes for internal hash modes

[Sasha Levin <sashal@kernel.org>]

From: Chen Cheng <chencheng@fnnas.com>

[ Upstream commit b2fd92f016e9d692fd3c8c08d0ee014e9212279d ]

dm-integrity direct, bitmap and inline internal-hash modes compute
integrity tags from the pages carried by the write bio.  The lower data
write also uses those pages, so the tag and the data write depend on the
same memory contents staying unchanged while writeback is in flight.

Without stable writes, a buffered writer can modify a writeback folio
after dm-integrity has submitted the data bio and before the lower device
has consumed the data.  After a crash, this can leave data from the later
contents with a tag calculated from the earlier contents, causing
permanent checksum failures on read.

Set BLK_FEAT_STABLE_WRITES for internal-hash D, B and I modes so
filesystems wait for writeback folios to become stable before modifying
them again.  Journal mode is left unchanged because it copies data into
the journal before computing and persisting the tag.

Tested using dm-delay over a virtio-blk test disk, dm-integrity
internal_hash:crc32c and no-journal ext4.  The D and B reproducers both
failed with checksum errors before this change and completed with
READ_RC=0 and zero mismatches after it.

Fixes: 7eada909bfd7 ("dm: add integrity target")
Cc: stable@vger.kernel.org
Reported-by: Sun Yangkai <sunyangkai@fygo.io>
Link: https://github.com/chencheng-fnnas/reproducer/blob/main/dm-integrity-writeback-race.py
Signed-off-by: Chen Cheng <chencheng@fnnas.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
[ sashal: adapted BLK_FEAT_STABLE_WRITES to QUEUE_FLAG_STABLE_WRITES using a new needs_stable_writes target bit. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/md/dm-integrity.c     | 3 +++
 drivers/md/dm-table.c         | 2 +-
 include/linux/device-mapper.h | 5 +++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index aa6f3e71c4fa2..d66eb4e36811a 100644
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -3515,6 +3515,9 @@ static void dm_integrity_io_hints(struct dm_target *ti, struct queue_limits *lim
 		limits->io_min = ic->sectors_per_block << SECTOR_SHIFT;
 		limits->dma_alignment = limits->logical_block_size - 1;
 	}
+
+	if (ic->internal_hash && (ic->mode == 'D' || ic->mode == 'B'))
+		ti->needs_stable_writes = true;
 }
 
 static void calculate_journal_section_size(struct dm_integrity_c *ic)
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index ed0a5e91968df..6d4ce9790a564 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1944,7 +1944,7 @@ static int device_requires_stable_pages(struct dm_target *ti,
 					struct dm_dev *dev, sector_t start,
 					sector_t len, void *data)
 {
-	return bdev_stable_writes(dev->bdev);
+	return ti->needs_stable_writes || bdev_stable_writes(dev->bdev);
 }
 
 int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 69d0435c7ebb0..f61daeeecee69 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -356,6 +356,11 @@ struct dm_target {
 	 */
 	bool discards_supported:1;
 
+	/*
+	 * Set if this target requires stable data during writeback.
+	 */
+	bool needs_stable_writes:1;
+
 	/*
 	 * Set if this target requires that discards be split on
 	 * 'max_discard_sectors' boundaries.
-- 
2.53.0