[PATCH v6 08/18] crypto: skcipher: Remove VLA usage for SKCIPHER_REQUEST_ON_STACK
From: Kees Cook <hidden>
Date: 2018-07-24 16:51:59
Also in:
dm-devel, linux-block, linux-crypto, linux-pm, linux-wireless, lkml
Subsystem:
crypto api, the rest · Maintainers:
Herbert Xu, "David S. Miller", Linus Torvalds
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@mail.gmail.com Signed-off-by: Kees Cook <redacted> --- 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..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 /**
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2.17.1