From 3195e0daf590683992edb4eed32269e569e04924 Mon Sep 17 00:00:00 2001 From: Ben Cressey Date: Tue, 15 Sep 2026 00:39:10 +0000 Subject: [PATCH] dm-crypt: reject the lmk IV mode with AEAD ciphers A "capi:" table line that pairs an AEAD cipher with the lmk IV mode, for example "capi:gcm(aes)-lmk" with the integrity:28:aead option, causes an oops when it is loaded. lmk sets tfms_count to 64, but crypt_alloc_tfms_aead only allocates one transform, so crypt_setkey reads past the end of the tfms_aead array and calls crypto_aead_setkey on the values it finds there. lmk exists for compatibility with Loop-AES, which uses CBC, so refuse it with an AEAD cipher rather than allocate 64 AEAD transforms. The check cannot go in crypt_iv_lmk_ctr with the other lmk checks, because the IV constructor runs after crypt_set_key. Note that this is not a security bug because the memory corruption can only be triggered by root. Fixes: 33d2f09fcb35 ("dm crypt: introduce new format of cipher with "capi:" prefix") Cc: stable@vger.kernel.org Signed-off-by: Ben Cressey Assisted-by: LLM Signed-off-by: Mikulas Patocka --- drivers/md/dm-crypt.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c index 9e170de50ad3..0bd22bda3e2d 100644 --- a/drivers/md/dm-crypt.c +++ b/drivers/md/dm-crypt.c @@ -2894,8 +2894,13 @@ static int crypt_ctr_cipher_new(struct dm_target *ti, char *cipher_in, char *key } } - if (*ivmode && !strcmp(*ivmode, "lmk")) + if (*ivmode && !strcmp(*ivmode, "lmk")) { + if (crypt_integrity_aead(cc)) { + ti->error = "AEAD transforms not supported for LMK"; + return -EINVAL; + } cc->tfms_count = 64; + } if (*ivmode && !strcmp(*ivmode, "essiv")) { if (!*ivopts) {