In the quest to remove all stack VLA usage from the kernel[1], this caps the skcipher request size similar to other limits and adds a sanity check at registration. In a manual review of the callers of crypto_skcipher_set_reqsize(), the largest was 384: 4 sun4i_cipher_req_ctx 6 safexcel_cipher_req 8 cryptd_skcipher_request_ctx 80 cipher_req_ctx 80 skcipher_request 96 crypto_rfc3686_req_ctx 104 nitrox_kcrypt_request 144 mv_cesa_skcipher_std_req 384 rctx [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: linux-crypto@xxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- include/crypto/internal/skcipher.h | 1 + include/crypto/skcipher.h | 4 +++- 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h index e42f7063f245..5035482cbe68 100644 --- a/include/crypto/internal/skcipher.h +++ b/include/crypto/internal/skcipher.h @@ -130,6 +130,7 @@ static inline struct crypto_skcipher *crypto_spawn_skcipher( static inline void crypto_skcipher_set_reqsize( struct crypto_skcipher *skcipher, unsigned int reqsize) { + BUG_ON(reqsize > SKCIPHER_MAX_REQSIZE); skcipher->reqsize = reqsize; } diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h index 2f327f090c3e..26eba8304d1d 100644 --- a/include/crypto/skcipher.h +++ b/include/crypto/skcipher.h @@ -139,9 +139,11 @@ struct skcipher_alg { struct crypto_alg base; }; +#define SKCIPHER_MAX_REQSIZE 384 + #define SKCIPHER_REQUEST_ON_STACK(name, tfm) \ char __##name##_desc[sizeof(struct skcipher_request) + \ - crypto_skcipher_reqsize(tfm)] CRYPTO_MINALIGN_ATTR; \ + SKCIPHER_MAX_REQSIZE] CRYPTO_MINALIGN_ATTR; \ struct skcipher_request *name = (void *)__##name##_desc /** -- 2.17.1
