crypto: api - Introduce generic max blocksize and alignmask (a9f7f88a) · Commits · 戴 / test

In the quest to remove all stack VLA usage from the kernel[1], this exposes a new general upper bound on crypto blocksize and alignmask (higher than for the existing cipher limits) for VLA removal, and introduces new checks. At present, the highest cra_alignmask in the kernel is 63. The highest cra_blocksize is 144 (SHA3_224_BLOCK_SIZE, 18 8-byte words). For the new blocksize limit, I went with 160 (20 8-byte words). [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>

crypto/algapi.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -57,9 +57,14 @@ static int crypto_check_alg(struct crypto_alg *alg)
		if (alg->cra_alignmask & (alg->cra_alignmask + 1))
		return -EINVAL;

		if (alg->cra_blocksize > PAGE_SIZE / 8)
		/* General maximums for all algs. */
		if (alg->cra_alignmask > MAX_ALGAPI_ALIGNMASK)
		return -EINVAL;

		if (alg->cra_blocksize > MAX_ALGAPI_BLOCKSIZE)
		return -EINVAL;

		/* Lower maximums for specific alg types. */
		if (!alg->cra_type && (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
		CRYPTO_ALG_TYPE_CIPHER) {
		if (alg->cra_alignmask > MAX_CIPHER_ALIGNMASK)

include/crypto/algapi.h

+3 −1

Original line number	Diff line number	Diff line
		@@ -20,8 +20,10 @@
		/*
		* Maximum values for blocksize and alignmask, used to allocate
		* static buffers that are big enough for any combination of
		* ciphers and architectures.
		* algs and architectures. Ciphers have a lower maximum size.
		*/
		#define MAX_ALGAPI_BLOCKSIZE 160
		#define MAX_ALGAPI_ALIGNMASK 63
		#define MAX_CIPHER_BLOCKSIZE 16
		#define MAX_CIPHER_ALIGNMASK 15

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