From: Ard Biesheuvel <ard.biesheu...@linaro.org>

In the quest to remove all stack VLA usage from the kernel[1], this
drops AHASH_REQUEST_ON_STACK by preallocated the ahash request area
with the skcipher area (which are not used at the same time).

[1] 
https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qpxydaacu1rq...@mail.gmail.com

Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 crypto/ccm.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/crypto/ccm.c b/crypto/ccm.c
index 0a083342ec8c..b242fd0d3262 100644
--- a/crypto/ccm.c
+++ b/crypto/ccm.c
@@ -50,7 +50,10 @@ struct crypto_ccm_req_priv_ctx {
        u32 flags;
        struct scatterlist src[3];
        struct scatterlist dst[3];
-       struct skcipher_request skreq;
+       union {
+               struct ahash_request ahreq;
+               struct skcipher_request skreq;
+       };
 };
 
 struct cbcmac_tfm_ctx {
@@ -181,7 +184,7 @@ static int crypto_ccm_auth(struct aead_request *req, struct 
scatterlist *plain,
        struct crypto_ccm_req_priv_ctx *pctx = crypto_ccm_reqctx(req);
        struct crypto_aead *aead = crypto_aead_reqtfm(req);
        struct crypto_ccm_ctx *ctx = crypto_aead_ctx(aead);
-       AHASH_REQUEST_ON_STACK(ahreq, ctx->mac);
+       struct ahash_request *ahreq = &pctx->ahreq;
        unsigned int assoclen = req->assoclen;
        struct scatterlist sg[3];
        u8 *odata = pctx->odata;
@@ -427,7 +430,7 @@ static int crypto_ccm_init_tfm(struct crypto_aead *tfm)
        crypto_aead_set_reqsize(
                tfm,
                align + sizeof(struct crypto_ccm_req_priv_ctx) +
-               crypto_skcipher_reqsize(ctr));
+               max(crypto_ahash_reqsize(mac), crypto_skcipher_reqsize(ctr)));
 
        return 0;
 
-- 
2.17.1

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