Re: [PATCH] crypto: qce - use the mapped scatterlist count for ahash requests

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [High] crypto: qce - wrong nents passed to dma_unmap_sg() in ahash
  paths
--

commit a88269ea6101fd18834fc68bd1c31da34ddad7a9
Author: Jinming Zhao <zhaojinming@uniontech.com>

crypto: qce - use the mapped scatterlist count for ahash requests

This commit stores the entry count returned by dma_map_sg() in
rctx->src_nents so that qce_dma_prep_sgs() and the subsequent dma_unmap_sg()
calls use the mapped scatterlist count.

Link: https://sashiko.dev/#/patchset/20261016-fix-qce-ccm-adata-leak-v1-0-f54a82af2de0@uniontech.com

> diff --git a/drivers/crypto/qce/sha.c b/drivers/crypto/qce/sha.c
> index b67d749db05f2..c53d0e53784e0 100644
> --- a/drivers/crypto/qce/sha.c
> +++ b/drivers/crypto/qce/sha.c
> @@ -97,6 +97,12 @@ static int qce_ahash_async_req_handle(struct crypto_async_request *async_req)
>  	if (!ret)
>  		return -EIO;
>  
> +	/*
> +	 * dma_map_sg() can coalesce entries, so use the number of mapped
> +	 * entries for the descriptor and for the later unmap.
> +	 */
> +	rctx->src_nents = ret;

[Severity: High]
Does overwriting rctx->src_nents pass the wrong entry count to
dma_unmap_sg()?

Both qce_ahash_done() and the error_unmap_src path pass rctx->src_nents to
dma_unmap_sg(), which the DMA API requires to be the original nents passed
to dma_map_sg() rather than the coalesced count it returned.  When
dma_map_sg() merges entries, unmapping with the smaller count triggers a
DMA-API debug warning and leaves trailing scatterlist segments unsynchronized
or unmapped.

Like qce_skcipher_async_req_handle(), keeping the return value of
dma_map_sg() in a local variable for qce_dma_prep_sgs() would preserve
rctx->src_nents for dma_unmap_sg().

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261113-qce-ahash-dma-count-v1-1-0423b54d75c8@uniontech.com?part=1