diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2025-11-14 16:54:01 +0100 |
|---|---|---|
| committer | Mikulas Patocka <mpatocka@redhat.com> | 2025-12-10 19:27:59 +0100 |
| commit | d9f3e47d3fae0c101d9094bc956ed24e7a0ee801 (patch) | |
| tree | a9982b1dfc4d624ab3d95f85eace50964f8329a7 | |
| parent | 7fa3e7d114abc9cc71cc35d768e116641074ddb4 (diff) | |
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>
| -rw-r--r-- | drivers/md/dm-verity-fec.c | 4 | ||||
| -rw-r--r-- | drivers/md/dm-verity-fec.h | 3 | ||||
| -rw-r--r-- | drivers/md/dm-verity-target.c | 2 |
3 files changed, 2 insertions, 7 deletions
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, |