From: Salvatore Mesoraca Subject: [PATCH 3/6] crypto: api - avoid VLA use Date: Sat, 7 Apr 2018 20:38:20 +0200 Message-ID: <1523126303-23205-4-git-send-email-s.mesoraca16@gmail.com> References: <1523126303-23205-1-git-send-email-s.mesoraca16@gmail.com> Cc: kernel-hardening@lists.openwall.com, linux-crypto@vger.kernel.org, "David S. Miller" , Herbert Xu , Kees Cook , Salvatore Mesoraca , Eric Biggers , Laura Abbott To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <1523126303-23205-1-git-send-email-s.mesoraca16@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org We avoid a VLA[1] by always allocating MAX_BLOCKSIZE + MAX_ALIGNMASK bytes. We also check the selected cipher at initialization time, if it doesn't comply with these limits, the initialization will fail. [1] http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Salvatore Mesoraca --- crypto/cipher.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/crypto/cipher.c b/crypto/cipher.c index 94fa355..9cedf23 100644 --- a/crypto/cipher.c +++ b/crypto/cipher.c @@ -67,7 +67,7 @@ static void cipher_crypt_unaligned(void (*fn)(struct crypto_tfm *, u8 *, { unsigned long alignmask = crypto_tfm_alg_alignmask(tfm); unsigned int size = crypto_tfm_alg_blocksize(tfm); - u8 buffer[size + alignmask]; + u8 buffer[MAX_BLOCKSIZE + MAX_ALIGNMASK]; u8 *tmp = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1); memcpy(tmp, src, size); @@ -105,9 +105,14 @@ static void cipher_decrypt_unaligned(struct crypto_tfm *tfm, int crypto_init_cipher_ops(struct crypto_tfm *tfm) { + const unsigned long alignmask = crypto_tfm_alg_alignmask(tfm); + const unsigned int size = crypto_tfm_alg_blocksize(tfm); struct cipher_tfm *ops = &tfm->crt_cipher; struct cipher_alg *cipher = &tfm->__crt_alg->cra_cipher; + if (size > MAX_BLOCKSIZE || alignmask > MAX_ALIGNMASK) + return -EINVAL; + ops->cit_setkey = setkey; ops->cit_encrypt_one = crypto_tfm_alg_alignmask(tfm) ? cipher_encrypt_unaligned : cipher->cia_encrypt; -- 1.9.1