On 06/20/2018 07:03 PM, Kees Cook wrote:
In the quest to remove all stack VLA usage from the kernel[1], this
removes the VLAs in SHASH_DESC_ON_STACK (via crypto_shash_descsize())
by using the maximum allowable size (which is now more clearly captured
in a macro). Similar limits are turned into macros as well.
[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Got the following warnings:
crypto/testmgr.c: In function ‘alg_test_crc32c.part.4’:
crypto/testmgr.c:1896:1: warning: the frame size of 2088 bytes is larger
than 1024 bytes [-Wframe-larger-than=]
crypto/hmac.c: In function ‘hmac_setkey’:
crypto/hmac.c:88:1: warning: the frame size of 2088 bytes is larger than
1024 bytes [-Wframe-larger-than=]
Christophe
---
crypto/shash.c | 6 +++---
include/crypto/hash.h | 6 +++++-
2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/crypto/shash.c b/crypto/shash.c
index 5d732c6bb4b2..ab6902c6dae7 100644
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -458,9 +458,9 @@ static int shash_prepare_alg(struct shash_alg *alg)
{
struct crypto_alg *base = &alg->base;
- if (alg->digestsize > PAGE_SIZE / 8 ||
- alg->descsize > PAGE_SIZE / 8 ||
- alg->statesize > PAGE_SIZE / 8)
+ if (alg->digestsize > SHASH_MAX_DIGESTSIZE ||
+ alg->descsize > SHASH_MAX_DESCSIZE ||
+ alg->statesize > SHASH_MAX_STATESIZE)
return -EINVAL;
base->cra_type = &crypto_shash_type;
diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index 76e432cab75d..308aad8bf523 100644
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -151,9 +151,13 @@ struct shash_desc {
void *__ctx[] CRYPTO_MINALIGN_ATTR;
};
+#define SHASH_MAX_DIGESTSIZE (PAGE_SIZE / 8)
+#define SHASH_MAX_DESCSIZE (PAGE_SIZE / 8)
+#define SHASH_MAX_STATESIZE (PAGE_SIZE / 8)
+
#define SHASH_DESC_ON_STACK(shash, ctx) \
char __##shash##_desc[sizeof(struct shash_desc) + \
- crypto_shash_descsize(ctx)] CRYPTO_MINALIGN_ATTR; \
+ SHASH_MAX_DESCSIZE] CRYPTO_MINALIGN_ATTR; \
struct shash_desc *shash = (struct shash_desc *)__##shash##_desc
/**
