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authorMarek Vasut <marex@denx.de>2014-03-14 05:37:04 +0400
committerHerbert Xu <herbert@gondor.apana.org.au>2014-03-21 17:54:20 +0400
commitab6bf4e5e5e4298e8649e635bee25542cccbfd97 (patch)
treeb28d2747b827c6ca66ab3445e737a5eaf3bb6209
parent85e0da925b2ddbf39a6cefb4e02ad51d0a0912c0 (diff)
downloadlinux-ab6bf4e5e5e4298e8649e635bee25542cccbfd97.tar.xz
crypto: hash - Fix the pointer voodoo in unaligned ahash
Add documentation for the pointer voodoo that is happening in crypto/ahash.c in ahash_op_unaligned(). This code is quite confusing, so add a beefy chunk of documentation. Moreover, make sure the mangled request is completely restored after finishing this unaligned operation. This means restoring all of .result, .base.data and .base.complete . Also, remove the crypto_completion_t complete = ... line present in the ahash_op_unaligned_done() function. This type actually declares a function pointer, which is very confusing. Finally, yet very important nonetheless, make sure the req->priv is free()'d only after the original request is restored in ahash_op_unaligned_done(). The req->priv data must not be free()'d before that in ahash_op_unaligned_finish(), since we would be accessing previously free()'d data in ahash_op_unaligned_done() and cause corruption. Signed-off-by: Marek Vasut <marex@denx.de> Cc: David S. Miller <davem@davemloft.net> Cc: Fabio Estevam <fabio.estevam@freescale.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Shawn Guo <shawn.guo@linaro.org> Cc: Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
-rw-r--r--crypto/ahash.c56
1 files changed, 49 insertions, 7 deletions
diff --git a/crypto/ahash.c b/crypto/ahash.c
index a92dc382f781..4fdb4d3fddec 100644
--- a/crypto/ahash.c
+++ b/crypto/ahash.c
@@ -201,22 +201,34 @@ static void ahash_op_unaligned_finish(struct ahash_request *req, int err)
memcpy(priv->result, req->result,
crypto_ahash_digestsize(crypto_ahash_reqtfm(req)));
+ /* Restore the original crypto request. */
+ req->result = priv->result;
+ req->base.complete = priv->complete;
+ req->base.data = priv->data;
+ req->priv = NULL;
+
+ /* Free the req->priv.priv from the ADJUSTED request. */
kzfree(priv);
}
static void ahash_op_unaligned_done(struct crypto_async_request *req, int err)
{
struct ahash_request *areq = req->data;
- struct ahash_request_priv *priv = areq->priv;
- crypto_completion_t complete = priv->complete;
- void *data = priv->data;
- ahash_op_unaligned_finish(areq, err);
+ /*
+ * Restore the original request, see ahash_op_unaligned() for what
+ * goes where.
+ *
+ * The "struct ahash_request *req" here is in fact the "req.base"
+ * from the ADJUSTED request from ahash_op_unaligned(), thus as it
+ * is a pointer to self, it is also the ADJUSTED "req" .
+ */
- areq->base.complete = complete;
- areq->base.data = data;
+ /* First copy areq->result into areq->priv.result */
+ ahash_op_unaligned_finish(areq, err);
- complete(&areq->base, err);
+ /* Complete the ORIGINAL request. */
+ areq->base.complete(&areq->base, err);
}
static int ahash_op_unaligned(struct ahash_request *req,
@@ -234,9 +246,39 @@ static int ahash_op_unaligned(struct ahash_request *req,
if (!priv)
return -ENOMEM;
+ /*
+ * WARNING: Voodoo programming below!
+ *
+ * The code below is obscure and hard to understand, thus explanation
+ * is necessary. See include/crypto/hash.h and include/linux/crypto.h
+ * to understand the layout of structures used here!
+ *
+ * The code here will replace portions of the ORIGINAL request with
+ * pointers to new code and buffers so the hashing operation can store
+ * the result in aligned buffer. We will call the modified request
+ * an ADJUSTED request.
+ *
+ * The newly mangled request will look as such:
+ *
+ * req {
+ * .result = ADJUSTED[new aligned buffer]
+ * .base.complete = ADJUSTED[pointer to completion function]
+ * .base.data = ADJUSTED[*req (pointer to self)]
+ * .priv = ADJUSTED[new priv] {
+ * .result = ORIGINAL(result)
+ * .complete = ORIGINAL(base.complete)
+ * .data = ORIGINAL(base.data)
+ * }
+ */
+
priv->result = req->result;
priv->complete = req->base.complete;
priv->data = req->base.data;
+ /*
+ * WARNING: We do not backup req->priv here! The req->priv
+ * is for internal use of the Crypto API and the
+ * user must _NOT_ _EVER_ depend on it's content!
+ */
req->result = PTR_ALIGN((u8 *)priv->ubuf, alignmask + 1);
req->base.complete = ahash_op_unaligned_done;