Re: [PATCH] bus: mhi: host: Add alignment check for event ring read pointer
From: Krishna Chaitanya Chundru
Date: Mon Oct 30 2023 - 02:31:05 EST
On 10/29/2023 12:56 PM, Manivannan Sadhasivam wrote:
On Fri, Oct 27, 2023 at 08:19:44AM -0600, Jeffrey Hugo wrote:
On 10/27/2023 7:09 AM, Manivannan Sadhasivam wrote:
On Mon, Oct 23, 2023 at 03:13:06PM +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_tre) aligned, an unaligned read pointer could lead
"mhi_tre" got renamed to "mhi_ring_element"
to multiple issues like DoS or ring buffer memory corruption.
So add a alignment check for event ring read pointer.
Since this is a potential fix, you should add the fixes tag and CC stable.
Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx>
---
drivers/bus/mhi/host/main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index 499590437e9b..c907bbb67fb2 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -268,7 +268,7 @@ 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 % 16 == 0;
How about,
!(addr % 16)
We are guaranteed that the ring allocation is 16 byte aligned, right?
I think using "struct mhi_ring_element" instead of "16" would be better.
I'm also thinking that perhaps doing a bit-wise & with a mask would be
better than the % operator. Not only is that how these alignment checks
seem to normally be done elsewhere, but this check is in a critical patch
for the MHI stack.
Yes, both of your suggestions sounds good to me.
Chaitanya, please use below check:
!(addr & (sizeof(struct mhi_ring_element) - 1))
- Mani
I will update in the next patch.
- Krishna Chaitanya.
-Jeff