Re: [PATCH] dmaengine: mmp_pdma: fix wrong sg length in mmp_pdma_prep_slave_sg

[Frank Li]

On Wed, Sep 09, 2026 at 11:38:41AM +0800, Baineng Shou wrote:

Need () for funciton mmp_pdma_prep_slave_sg()

Frank

>
> In mmp_pdma_prep_slave_sg(), for_each_sg() iterates the scatterlist
> putting each entry into 'sg', but the entry length is read from 'sgl'
> (the list head) instead of 'sg' (the current entry):
>
>     for_each_sg(sgl, sg, sg_len, i) {
>         addr = sg_dma_address(sg);
>         avail = sg_dma_len(sgl);   /* should be 'sg' */
>
> Consequently 'avail' is always the length of the first entry. For
> multi-sg lists this causes out-of-bounds reads when a later entry is
> shorter than the first, and silent data loss when it is longer.
> Single-sg or uniformly-sized lists happen to mask the issue.
>
> Fixes: c8acd6aa6bed3 ("dmaengine: mmp-pdma support")
> Signed-off-by: Baineng Shou <shoubaineng@xxxxxxxxx>
> ---
>  drivers/dma/mmp_pdma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma/mmp_pdma.c b/drivers/dma/mmp_pdma.c
> index 386e85cd4882..e90fd2023af7 100644
> --- a/drivers/dma/mmp_pdma.c
> +++ b/drivers/dma/mmp_pdma.c
> @@ -713,7 +713,7 @@ mmp_pdma_prep_slave_sg(struct dma_chan *dchan, struct scatterlist *sgl,
>
>         for_each_sg(sgl, sg, sg_len, i) {
>                 addr = sg_dma_address(sg);
> -               avail = sg_dma_len(sgl);
> +               avail = sg_dma_len(sg);
>
>                 do {
>                         len = min_t(size_t, avail, PDMA_MAX_DESC_BYTES);
> --
> 2.34.1
>