FAILED: patch "[PATCH] dm integrity: fix memory corruption when tag_size is less" failed to apply to 4.19-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 08c1af8f1c13bbf210f1760132f4df24d0ed46d6 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Sun, 3 Apr 2022 14:38:22 -0400
Subject: [PATCH] dm integrity: fix memory corruption when tag_size is less
 than digest size

It is possible to set up dm-integrity in such a way that the
"tag_size" parameter is less than the actual digest size. In this
situation, a part of the digest beyond tag_size is ignored.

In this case, dm-integrity would write beyond the end of the
ic->recalc_tags array and corrupt memory. The corruption happened in
integrity_recalc->integrity_sector_checksum->crypto_shash_final.

Fix this corruption by increasing the tags array so that it has enough
padding at the end to accomodate the loop in integrity_recalc() being
able to write a full digest size for the last member of the tags
array.

Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index ad2d5faa2ebb..36ae30b73a6e 100644
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -4399,6 +4399,7 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	}
 
 	if (ic->internal_hash) {
+		size_t recalc_tags_size;
 		ic->recalc_wq = alloc_workqueue("dm-integrity-recalc", WQ_MEM_RECLAIM, 1);
 		if (!ic->recalc_wq ) {
 			ti->error = "Cannot allocate workqueue";
@@ -4412,8 +4413,10 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 			r = -ENOMEM;
 			goto bad;
 		}
-		ic->recalc_tags = kvmalloc_array(RECALC_SECTORS >> ic->sb->log2_sectors_per_block,
-						 ic->tag_size, GFP_KERNEL);
+		recalc_tags_size = (RECALC_SECTORS >> ic->sb->log2_sectors_per_block) * ic->tag_size;
+		if (crypto_shash_digestsize(ic->internal_hash) > ic->tag_size)
+			recalc_tags_size += crypto_shash_digestsize(ic->internal_hash) - ic->tag_size;
+		ic->recalc_tags = kvmalloc(recalc_tags_size, GFP_KERNEL);
 		if (!ic->recalc_tags) {
 			ti->error = "Cannot allocate tags for recalculating";
 			r = -ENOMEM;