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 <ma...@denx.de> Cc: David S. Miller <da...@davemloft.net> Cc: Fabio Estevam <fabio.este...@freescale.com> Cc: Herbert Xu <herb...@gondor.apana.org.au> Cc: Shawn Guo <shawn....@linaro.org> Cc: Tom Lendacky <thomas.lenda...@amd.com> --- crypto/ahash.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 49 insertions(+), 7 deletions(-) V2: Move the restoration of the ORIGINAL crypto request fields from ahash_op_unaligned_done() to ahash_op_unaligned_finish(). This way, we handle both Sync-HASH and Async-HASH cases properly: SYNC: ahash_op_unaligned_finish() is called with err=0 . Data are copied from ADJUSTED request to ORIGINAL request, ORIGINAL request is correctly restored and free'd. ASYNC: ahash_op_unaligned_finish() is called with err=-EINPROGRESS, returns. Later, ahash_op_unaligned_finish() is called again from ahash_op_unaligned_done() callback. Data are copied from ADJUSTED request to ORIGINAL request, ORIGINAL request is correctly restored and free'd. V3: Swap the names of req<->areq variables to be consistent with the rest of the crypto API again. V4: Do not save (struct ahash_request).priv when adjusting the request, the .priv field is internal to Crypto API and the user must NOT EVER use it. Add a comment about this. diff --git a/crypto/ahash.c b/crypto/ahash.c index a92dc38..4fdb4d3 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; -- 1.8.5.2 -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html