| Message ID | 20180717042150.37761-11-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
On Mon, Jul 16, 2018 at 09:21:49PM -0700, Kees Cook wrote: > 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 initialization. AHASH_REQUEST_ON_STACK is special, though: it > is only ever used for shash-wrapped ahash, so its size is bounded only > by non-async hashes. A manual inspection of this shows the largest to be: > sizeof(struct shash_desc) + SHASH_MAX_DESCSIZE > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > crypto/shash.c | 9 ++++++++- > include/crypto/hash.h | 10 +++++++++- > 2 files changed, 17 insertions(+), 2 deletions(-) > > diff --git a/crypto/shash.c b/crypto/shash.c > index 8d4746b14dd5..e344560458cb 100644 > --- a/crypto/shash.c > +++ b/crypto/shash.c > @@ -355,6 +355,7 @@ int crypto_init_shash_ops_async(struct crypto_tfm *tfm) > struct crypto_ahash *crt = __crypto_ahash_cast(tfm); > struct crypto_shash **ctx = crypto_tfm_ctx(tfm); > struct crypto_shash *shash; > + size_t reqsize; > > if (!crypto_mod_get(calg)) > return -EAGAIN; > @@ -365,6 +366,12 @@ int crypto_init_shash_ops_async(struct crypto_tfm *tfm) > return PTR_ERR(shash); > } > > + reqsize = sizeof(struct shash_desc) + crypto_shash_descsize(shash); > + if (WARN_ON(reqsize > AHASH_MAX_REQSIZE)) { > + crypto_mod_put(calg); > + return -EINVAL; > + } 'crypto_free_shash(shash);' instead of 'crypto_mod_put(calg);' - Eric -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
On Tue, Jul 17, 2018 at 9:43 AM, Eric Biggers <ebiggers3@gmail.com> wrote: > On Mon, Jul 16, 2018 at 09:21:49PM -0700, Kees Cook wrote: >> + reqsize = sizeof(struct shash_desc) + crypto_shash_descsize(shash); >> + if (WARN_ON(reqsize > AHASH_MAX_REQSIZE)) { >> + crypto_mod_put(calg); >> + return -EINVAL; >> + } > > 'crypto_free_shash(shash);' instead of 'crypto_mod_put(calg);' Oops! Yes, thanks; I have fixed it now in the next version. -Kees
diff --git a/crypto/shash.c b/crypto/shash.c index 8d4746b14dd5..e344560458cb 100644 --- a/crypto/shash.c +++ b/crypto/shash.c @@ -355,6 +355,7 @@ int crypto_init_shash_ops_async(struct crypto_tfm *tfm) struct crypto_ahash *crt = __crypto_ahash_cast(tfm); struct crypto_shash **ctx = crypto_tfm_ctx(tfm); struct crypto_shash *shash; + size_t reqsize; if (!crypto_mod_get(calg)) return -EAGAIN; @@ -365,6 +366,12 @@ int crypto_init_shash_ops_async(struct crypto_tfm *tfm) return PTR_ERR(shash); } + reqsize = sizeof(struct shash_desc) + crypto_shash_descsize(shash); + if (WARN_ON(reqsize > AHASH_MAX_REQSIZE)) { + crypto_mod_put(calg); + return -EINVAL; + } + *ctx = shash; tfm->exit = crypto_exit_shash_ops_async; @@ -383,7 +390,7 @@ int crypto_init_shash_ops_async(struct crypto_tfm *tfm) if (alg->import) crt->import = shash_async_import; - crt->reqsize = sizeof(struct shash_desc) + crypto_shash_descsize(shash); + crt->reqsize = reqsize; return 0; } diff --git a/include/crypto/hash.h b/include/crypto/hash.h index 4fcd0e2368cd..2181fb38eab9 100644 --- a/include/crypto/hash.h +++ b/include/crypto/hash.h @@ -67,9 +67,17 @@ struct ahash_request { #define AHASH_MAX_DIGESTSIZE 512 #define AHASH_MAX_STATESIZE 512 +/* + * HASH_REQUEST_ON_STACK must only be used when wrapping shash (i.e. + * allocated with a CRYPTO_ALG_ASYNC mask), and is generally discouraged + * (just use shash directly). This is really only ever needed when using + * scatter/gather input sources. + */ +#define AHASH_MAX_REQSIZE (sizeof(struct shash_desc) + \ + SHASH_MAX_DESCSIZE) #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 /**
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 initialization. AHASH_REQUEST_ON_STACK is special, though: it is only ever used for shash-wrapped ahash, so its size is bounded only by non-async hashes. A manual inspection of this shows the largest to be: sizeof(struct shash_desc) + SHASH_MAX_DESCSIZE [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook <keescook@chromium.org> --- crypto/shash.c | 9 ++++++++- include/crypto/hash.h | 10 +++++++++- 2 files changed, 17 insertions(+), 2 deletions(-)