| Message ID | 20180807211843.47586-10-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
| Series | crypto: Remove VLA usage | expand |
On Tue, Aug 07, 2018 at 02:18:43PM -0700, Kees Cook wrote: > 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 <keescook@chromium.org> > --- > 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); Please do not add these BUG_ONs. Instead allow this function to fail and check for the failure in the caller. Thanks,
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 /**
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 <keescook@chromium.org> --- include/crypto/internal/skcipher.h | 1 + include/crypto/skcipher.h | 4 +++- 2 files changed, 4 insertions(+), 1 deletion(-)