On Fri, May 31, 2024 at 2:46 PM Peter Maydell <peter.mayd...@linaro.org>
wrote:
> In fdf029762f501 we factored out the handling of reading and writing
> DMA descriptors from guest memory. Unfortunately we accidentally
> made the descriptor-read read the descriptor into the address of the
> buffer rather than into the buffer, because we didn't notice we
> needed to update the arguments to the dma_memory_read() call. Before
> the refactoring, "&desc" is the address of a local struct DPDMADescriptor
> variable in xlnx_dpdma_start_operation(), which is the correct target
> for the guest-memory-read. But after the refactoring 'desc' is the
> "DPDMADescriptor *desc" argument to the new function, and so it is
> already an address.
>
> This bug is an overrun of a stack variable, since a pointer is at
> most 8 bytes long and we try to read 64 bytes, as well as being
> incorrect behaviour.
>
> Pass 'desc' rather than '&desc' as the dma_memory_read() argument
> to fix this.
>
> (The same bug is not present in xlnx_dpdma_write_descriptor(),
> because there we are writing the descriptor from a local struct
> variable "DPDMADescriptor tmp_desc" and so passing &tmp_desc to
> dma_memory_write() is correct.)
>
> Spotted by Coverity: CID 1546649
>
>
+ CC Fred.
Reviewed-by: Edgar E. Iglesias <edgar.igles...@amd.com>
> Fixes: fdf029762f50101 ("xlnx_dpdma: fix descriptor endianness bug")
> Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
> ---
> hw/dma/xlnx_dpdma.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/dma/xlnx_dpdma.c b/hw/dma/xlnx_dpdma.c
> index dde4aeca401..a685bd28bb8 100644
> --- a/hw/dma/xlnx_dpdma.c
> +++ b/hw/dma/xlnx_dpdma.c
> @@ -619,7 +619,7 @@ static MemTxResult
> xlnx_dpdma_read_descriptor(XlnxDPDMAState *s,
> DPDMADescriptor *desc)
> {
> MemTxResult res = dma_memory_read(&address_space_memory, desc_addr,
> - &desc, sizeof(DPDMADescriptor),
> + desc, sizeof(DPDMADescriptor),
> MEMTXATTRS_UNSPECIFIED);
> if (res) {
> return res;
> --
> 2.34.1
>
>
