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. Looking at instrumented tcrypt output, the largest is for lrw: crypt: testing lrw(aes) crypto_skcipher_set_reqsize: 8 crypto_skcipher_set_reqsize: 88 crypto_skcipher_set_reqsize: 472 [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- include/crypto/internal/skcipher.h | 3 +++ include/crypto/skcipher.h | 4 +++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h index d2926ecae2ac..6da811c0747e 100644 --- a/include/crypto/internal/skcipher.h +++ b/include/crypto/internal/skcipher.h @@ -130,6 +130,9 @@ static inline struct crypto_skcipher *crypto_spawn_skcipher( static inline int crypto_skcipher_set_reqsize( struct crypto_skcipher *skcipher, unsigned int reqsize) { + if (WARN_ON(reqsize > SKCIPHER_MAX_REQSIZE)) + return -EINVAL; + skcipher->reqsize = reqsize; return 0; diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h index 2f327f090c3e..c48e194438cf 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 472 + #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
