[PATCH v4.19-v5.10] block: initialize integrity buffer to zero before writing it to media

[Shivani Agarwal <shivani.agarwal@broadcom.com>]

From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 899ee2c3829c5ac14bfc7d3c4a5846c0b709b78f ]

Metadata added by bio_integrity_prep is using plain kmalloc, which leads
to random kernel memory being written media.  For PI metadata this is
limited to the app tag that isn't used by kernel generated metadata,
but for non-PI metadata the entire buffer leaks kernel memory.

Fix this by adding the __GFP_ZERO flag to allocations for writes.

Fixes: 7ba1ba12eeef ("block: Block layer data integrity support")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20240613084839.1044015-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Shivani Agarwal <shivani.agarwal@broadcom.com>
---
 block/bio-integrity.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index a4cfc9727..499697330 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -216,6 +216,7 @@ bool bio_integrity_prep(struct bio *bio)
 	unsigned int bytes, offset, i;
 	unsigned int intervals;
 	blk_status_t status;
+	gfp_t gfp = GFP_NOIO;
 
 	if (!bi)
 		return true;
@@ -238,12 +239,20 @@ bool bio_integrity_prep(struct bio *bio)
 		if (!bi->profile->generate_fn ||
 		    !(bi->flags & BLK_INTEGRITY_GENERATE))
 			return true;
+
+		/*
+		 * Zero the memory allocated to not leak uninitialized kernel
+		 * memory to disk.  For PI this only affects the app tag, but
+		 * for non-integrity metadata it affects the entire metadata
+		 * buffer.
+		 */
+		gfp |= __GFP_ZERO;
 	}
 	intervals = bio_integrity_intervals(bi, bio_sectors(bio));
 
 	/* Allocate kernel buffer for protection data */
 	len = intervals * bi->tuple_size;
-	buf = kmalloc(len, GFP_NOIO | q->bounce_gfp);
+	buf = kmalloc(len, gfp | q->bounce_gfp);
 	status = BLK_STS_RESOURCE;
 	if (unlikely(buf == NULL)) {
 		printk(KERN_ERR "could not allocate integrity buffer\n");
-- 
2.39.4