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crypto: xcbc - Remove VLA usage 

In the quest to remove all stack VLA usage from the kernel[1], this uses
the maximum blocksize and adds a sanity check. For xcbc, the blocksize
must always be 16, so use that, since it's already being enforced during
instantiation.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Kees Cook 2018-08-07 14:18:35 -07:00 committed by Herbert Xu
parent 578bdaabd0
commit 3bdd23f886
1 changed files with 5 additions and 3 deletions
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8
crypto/xcbc.c
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@ -57,15 +57,17 @@ struct xcbc_desc_ctx {
u8 ctx[]; u8 ctx[];
}; };
#define XCBC_BLOCKSIZE 16
static int crypto_xcbc_digest_setkey(struct crypto_shash *parent, static int crypto_xcbc_digest_setkey(struct crypto_shash *parent,
const u8 *inkey, unsigned int keylen) const u8 *inkey, unsigned int keylen)
{ {
unsigned long alignmask = crypto_shash_alignmask(parent); unsigned long alignmask = crypto_shash_alignmask(parent);
struct xcbc_tfm_ctx *ctx = crypto_shash_ctx(parent); struct xcbc_tfm_ctx *ctx = crypto_shash_ctx(parent);
int bs = crypto_shash_blocksize(parent);
u8 *consts = PTR_ALIGN(&ctx->ctx[0], alignmask + 1); u8 *consts = PTR_ALIGN(&ctx->ctx[0], alignmask + 1);
int err = 0; int err = 0;
u8 key1[bs]; u8 key1[XCBC_BLOCKSIZE];
int bs = sizeof(key1);
if ((err = crypto_cipher_setkey(ctx->child, inkey, keylen))) if ((err = crypto_cipher_setkey(ctx->child, inkey, keylen)))
return err; return err;
@ -212,7 +214,7 @@ static int xcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
return PTR_ERR(alg); return PTR_ERR(alg);
switch(alg->cra_blocksize) { switch(alg->cra_blocksize) {
case 16: case XCBC_BLOCKSIZE:
break; break;
default: default:
goto out_put_alg; goto out_put_alg;