On Sun, Mar 26, 2023 at 11:52:23AM -0500, Alex Elder wrote:
> In gsi_trans_pool_init_dma(), the total size of a pool of memory
> used for DMA transactions is calculated. However the calculation is
> done incorrectly.
>
> For 4KB pages, this total size is currently always more than one
> page, and as a result, the calculation produces a positive (though
> incorrect) total size. The code still works in this case; we just
> end up with fewer DMA pool entries than we intended.
>
> Bjorn Andersson tested booting a kernel with 16KB pages, and hit a
> null pointer derereference in sg_alloc_append_table_from_pages(),
> descending from gsi_trans_pool_init_dma(). The cause of this was
> that a 16KB total size was going to be allocated, and with 16KB
> pages the order of that allocation is 0. The total_size calculation
> yielded 0, which eventually led to the crash.
>
> Correcting the total_size calculation fixes the problem.
>
> Reported-by: <quic_bjorande@xxxxxxxxxxx>
> Tested-by: <quic_bjorande@xxxxxxxxxxx>
It would be nice to add "Bjorn Andersson" to these two.
Regards,
Bjorn
> Fixes: 9dd441e4ed57 ("soc: qcom: ipa: GSI transactions")
> Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
> ---
> drivers/net/ipa/gsi_trans.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ipa/gsi_trans.c b/drivers/net/ipa/gsi_trans.c
> index 0f52c068c46d6..ee6fb00b71eb6 100644
> --- a/drivers/net/ipa/gsi_trans.c
> +++ b/drivers/net/ipa/gsi_trans.c
> @@ -156,7 +156,7 @@ int gsi_trans_pool_init_dma(struct device *dev, struct gsi_trans_pool *pool,
> * gsi_trans_pool_exit_dma() can assume the total allocated
> * size is exactly (count * size).
> */
> - total_size = get_order(total_size) << PAGE_SHIFT;
> + total_size = PAGE_SIZE << get_order(total_size);
>
> virt = dma_alloc_coherent(dev, total_size, &addr, GFP_KERNEL);
> if (!virt)
> --
> 2.34.1
>
