Commit d9f3e47d3fae for kernel

commit d9f3e47d3fae0c101d9094bc956ed24e7a0ee801
Author: Mikulas Patocka <mpatocka@redhat.com>
Date:   Fri Nov 14 16:54:01 2025 +0100

    dm-verity: disable recursive forward error correction

    There are two problems with the recursive correction:

    1. It may cause denial-of-service. In fec_read_bufs, there is a loop that
    has 253 iterations. For each iteration, we may call verity_hash_for_block
    recursively. There is a limit of 4 nested recursions - that means that
    there may be at most 253^4 (4 billion) iterations. Red Hat QE team
    actually created an image that pushes dm-verity to this limit - and this
    image just makes the udev-worker process get stuck in the 'D' state.

    2. It doesn't work. In fec_read_bufs we store data into the variable
    "fio->bufs", but fio bufs is shared between recursive invocations, if
    "verity_hash_for_block" invoked correction recursively, it would
    overwrite partially filled fio->bufs.

    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
    Reported-by: Guangwu Zhang <guazhang@redhat.com>
    Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
    Reviewed-by: Eric Biggers <ebiggers@kernel.org>

diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
index d792eaed0792..9dbb68c9afe4 100644
--- a/drivers/md/dm-verity-fec.c
+++ b/drivers/md/dm-verity-fec.c
@@ -418,10 +418,8 @@ int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
 	if (!verity_fec_is_enabled(v))
 		return -EOPNOTSUPP;

-	if (fio->level >= DM_VERITY_FEC_MAX_RECURSION) {
-		DMWARN_LIMIT("%s: FEC: recursion too deep", v->data_dev->name);
+	if (fio->level)
 		return -EIO;
-	}

 	fio->level++;

diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h
index dd55037377b6..f0e991a613f0 100644
--- a/drivers/md/dm-verity-fec.h
+++ b/drivers/md/dm-verity-fec.h
@@ -23,9 +23,6 @@
 #define DM_VERITY_FEC_BUF_MAX \
 	(1 << (PAGE_SHIFT - DM_VERITY_FEC_BUF_RS_BITS))

-/* maximum recursion level for verity_fec_decode */
-#define DM_VERITY_FEC_MAX_RECURSION	4
-
 #define DM_VERITY_OPT_FEC_DEV		"use_fec_from_device"
 #define DM_VERITY_OPT_FEC_BLOCKS	"fec_blocks"
 #define DM_VERITY_OPT_FEC_START		"fec_start"
diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 52a0e052a5e8..5c17472d7896 100644
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -1789,7 +1789,7 @@ static struct target_type verity_target = {
 	.name		= "verity",
 /* Note: the LSMs depend on the singleton and immutable features */
 	.features	= DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
-	.version	= {1, 12, 0},
+	.version	= {1, 13, 0},
 	.module		= THIS_MODULE,
 	.ctr		= verity_ctr,
 	.dtr		= verity_dtr,