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    Subject[PATCH 10/11] crypto: ahash: Remove VLA usage for AHASH_REQUEST_ON_STACK
    Date
    In the quest to remove all stack VLA usage from the kernel[1], this caps
    the ahash request size similar to the other limits and adds a sanity
    check at registration.

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

    Signed-off-by: Kees Cook <keescook@chromium.org>
    ---
    include/crypto/hash.h | 3 ++-
    include/crypto/internal/hash.h | 1 +
    2 files changed, 3 insertions(+), 1 deletion(-)

    diff --git a/include/crypto/hash.h b/include/crypto/hash.h
    index b9df568dc98e..7d62309baf0b 100644
    --- a/include/crypto/hash.h
    +++ b/include/crypto/hash.h
    @@ -66,10 +66,11 @@ struct ahash_request {

    #define AHASH_MAX_DIGESTSIZE (PAGE_SIZE / 8)
    #define AHASH_MAX_STATESIZE (PAGE_SIZE / 8)
    +#define AHASH_MAX_REQSIZE (PAGE_SIZE / 8)

    #define AHASH_REQUEST_ON_STACK(name, ahash) \
    char __##name##_desc[sizeof(struct ahash_request) + \
    - crypto_ahash_reqsize(ahash)] CRYPTO_MINALIGN_ATTR; \
    + AHASH_MAX_REQSIZE] CRYPTO_MINALIGN_ATTR; \
    struct ahash_request *name = (void *)__##name##_desc

    /**
    diff --git a/include/crypto/internal/hash.h b/include/crypto/internal/hash.h
    index a0b0ad9d585e..d96ae5f52125 100644
    --- a/include/crypto/internal/hash.h
    +++ b/include/crypto/internal/hash.h
    @@ -142,6 +142,7 @@ static inline struct ahash_alg *__crypto_ahash_alg(struct crypto_alg *alg)
    static inline void crypto_ahash_set_reqsize(struct crypto_ahash *tfm,
    unsigned int reqsize)
    {
    + BUG_ON(reqsize > AHASH_MAX_REQSIZE);
    tfm->reqsize = reqsize;
    }

    --
    2.17.1
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