Re: [PATCH v2] bus: mhi: host: Add alignment check for event ring read pointer

[Krishna Chaitanya Chundru]

On 11/1/2023 10:47 AM, Manivannan Sadhasivam wrote:
> On Tue, Oct 31, 2023 at 03:21:05PM +0530, Krishna chaitanya chundru wrote:
> > Though we do check the event ring read pointer by "is_valid_ring_ptr"
> > to make sure it is in the buffer range, but there is another risk the
> > pointer may be not aligned.  Since we are expecting event ring elements
> > are 128 bits(struct mhi_ring_element) aligned, an unaligned read pointer
> > could lead to multiple issues like DoS or ring buffer memory corruption.
> >
> > So add a alignment check for event ring read pointer.
> >
> > Fixes: ec32332df764 ("bus: mhi: core: Sanity check values from remote device before use")
> > cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
>
> Bjorn gave his R-b tag for v1 and you didn't include it. If you dropped it on
> purpose, then you should mention it in the "Changes" along with a justification.
>
> - Mani

As there is change in the logic I didn't include the tag. I will mention 
this on the next patch.

- Krishna Chaitanya.

> > ---
> > Changes in v2:
> > - Change the modulus operation to bit-wise & operation as suggested by Jeff.
> > - Link to v1: https://lore.kernel.org/r/20231023-alignment_check-v1-1-2ca5716d5c15@xxxxxxxxxxx
> > ---
> >   drivers/bus/mhi/host/main.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
> > index 499590437e9b..e765c16a99d1 100644
> > --- a/drivers/bus/mhi/host/main.c
> > +++ b/drivers/bus/mhi/host/main.c
> > @@ -268,7 +268,8 @@ static void mhi_del_ring_element(struct mhi_controller *mhi_cntrl,
> >   
> >   static bool is_valid_ring_ptr(struct mhi_ring *ring, dma_addr_t addr)
> >   {
> > -	return addr >= ring->iommu_base && addr < ring->iommu_base + ring->len;
> > +	return addr >= ring->iommu_base && addr < ring->iommu_base + ring->len &&
> > +			!(addr & (sizeof(struct mhi_ring_element) - 1));
> >   }
> >   
> >   int mhi_destroy_device(struct device *dev, void *data)
> >
> > ---
> > base-commit: 71e68e182e382e951d6248bccc3c960dcec5a718
> > change-id: 20231013-alignment_check-c013f509d24a
> >
> > Best regards,
> > --
> > Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>