dm integrity: fix memory corruption when tag_size is less than digest size

commit 08c1af8f1c13bbf210f1760132f4df24d0ed46d6 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index cffd423172726b1bca0c7baeea950d8ffaf85305..b0105d53918abb445ad91c97218e4eda85b0e0d9 100644 (file)
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -3504,6 +3504,7 @@ try_smaller_buffer:
        }
 
        if (ic->sb->flags & cpu_to_le32(SB_FLAG_RECALCULATING)) {
+               size_t recalc_tags_size;
                if (!ic->internal_hash) {
                        r = -EINVAL;
                        ti->error = "Recalculate is only valid with internal hash";
@@ -3522,8 +3523,10 @@ try_smaller_buffer:
                        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;