Re: [PATCH] crypto: mxs-dcp: handle zero-length skcipher requests

在 2026/8/29 3:25, Frank Li 写道:

On Fri, Aug 28, 2026 at 05:32:09PM +0800, Linmao Li wrote:

quoted

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Zero-length skcipher requests are valid no-ops, but MXS-DCP queues them.

Any document show it? if return 0 when cryptelen, it is async, no
call crypto_request_complete.

   Yes. CRYPTO_ALG_ASYNC means that the implementation may complete a
   request asynchronously, not that every request must do so.

   A return value of 0 indicates synchronous completion.  Only
   -EINPROGRESS and -EBUSY cause crypto_wait_req() to wait for the
   completion callback.  The existing fallback path relies on the same
   semantics.

   There is also a direct precedent in commit 8a4e047c6cc0
   ("crypto: marvell/cesa - Handle zero-length skcipher requests").
   Marvell CESA registers asynchronous skcipher algorithms but handles a
   zero-length request with:

           if (!req->cryptlen)
                   return 0;


Thanks,
Linmao

Frank

quoted

When such a request reaches the worker, last_out_len remains zero. The
CBC completion path then subtracts AES_BLOCK_SIZE from this unsigned
value when updating the IV, causing the offset to underflow. On
decryption, the resulting source address precedes aes_in_buf.

Return success before enqueueing zero-length requests. This avoids the
invalid source access and leaves the IV unchanged for a no-op.

Fixes: fadd7a6e616b ("crypto: mxs-dcp - Fix AES issues")
Signed-off-by: Linmao Li <redacted>
---
  drivers/crypto/mxs-dcp.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/drivers/crypto/mxs-dcp.c b/drivers/crypto/mxs-dcp.c
index 133ebc998236..60794b4d49fa 100644
--- a/drivers/crypto/mxs-dcp.c
+++ b/drivers/crypto/mxs-dcp.c

@@ -473,6 +473,9 @@ static int mxs_dcp_aes_enqueue(struct skcipher_request *req, int enc, int ecb)
         struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req);
         int ret;

+       if (!req->cryptlen)
+               return 0;
+
         if (unlikely(actx->key_len != AES_KEYSIZE_128 && !actx->key_referenced))
                 return mxs_dcp_block_fallback(req, enc);

base-commit: 8d3ae59288f1e7d58d76558a6ee96d533bc5019f
--
2.25.1