crypto: hash - Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this
removes the VLAs in SHASH_DESC_ON_STACK (via crypto_shash_descsize())
by using the maximum allowable size (which is now more clearly captured
in a macro), along with a few other cases. Similar limits are turned into
macros as well.

A review of existing sizes shows that SHA512_DIGEST_SIZE (64) is the
largest digest size and that sizeof(struct sha3_state) (360) is the
largest descriptor size. The corresponding maximums are reduced.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/ahash.c b/crypto/ahash.c
index a64c143..78aaf21 100644 (file)
--- a/crypto/ahash.c
+++ b/crypto/ahash.c
@@ -550,8 +550,8 @@ static int ahash_prepare_alg(struct ahash_alg *alg)
 {
        struct crypto_alg *base = &alg->halg.base;
 
-       if (alg->halg.digestsize > PAGE_SIZE / 8 ||
-           alg->halg.statesize > PAGE_SIZE / 8 ||
+       if (alg->halg.digestsize > HASH_MAX_DIGESTSIZE ||
+           alg->halg.statesize > HASH_MAX_STATESIZE ||
            alg->halg.statesize == 0)
                return -EINVAL;
 

diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index bfcf595..d0cde54 100644 (file)
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -239,7 +239,7 @@ static int hash_accept(struct socket *sock, struct socket *newsock, int flags,
        struct alg_sock *ask = alg_sk(sk);
        struct hash_ctx *ctx = ask->private;
        struct ahash_request *req = &ctx->req;
-       char state[crypto_ahash_statesize(crypto_ahash_reqtfm(req)) ? : 1];
+       char state[HASH_MAX_STATESIZE];
        struct sock *sk2;
        struct alg_sock *ask2;
        struct hash_ctx *ctx2;

diff --git a/crypto/shash.c b/crypto/shash.c
index 5d732c6..86d76b5 100644 (file)
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -458,9 +458,9 @@ static int shash_prepare_alg(struct shash_alg *alg)
 {
        struct crypto_alg *base = &alg->base;
 
-       if (alg->digestsize > PAGE_SIZE / 8 ||
-           alg->descsize > PAGE_SIZE / 8 ||
-           alg->statesize > PAGE_SIZE / 8)
+       if (alg->digestsize > HASH_MAX_DIGESTSIZE ||
+           alg->descsize > HASH_MAX_DESCSIZE ||
+           alg->statesize > HASH_MAX_STATESIZE)
                return -EINVAL;
 
        base->cra_type = &crypto_shash_type;

diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index 76e432c..2158701 100644 (file)
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -151,9 +151,13 @@ struct shash_desc {
        void *__ctx[] CRYPTO_MINALIGN_ATTR;
 };
 
+#define HASH_MAX_DIGESTSIZE     64
+#define HASH_MAX_DESCSIZE      360
+#define HASH_MAX_STATESIZE     512
+
 #define SHASH_DESC_ON_STACK(shash, ctx)                                  \
        char __##shash##_desc[sizeof(struct shash_desc) +         \
-               crypto_shash_descsize(ctx)] CRYPTO_MINALIGN_ATTR; \
+               HASH_MAX_DESCSIZE] CRYPTO_MINALIGN_ATTR; \
        struct shash_desc *shash = (struct shash_desc *)__##shash##_desc
 
 /**