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

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Date:   Fri, 27 Oct 2023 18:39:47 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>
Cc:     mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, quic_vbadigan@...cinc.com,
        quic_ramkri@...cinc.com, quic_skananth@...cinc.com,
        quic_parass@...cinc.com
Subject: Re: [PATCH] bus: mhi: host: Add alignment check for event ring read
 pointer

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@...cinc.com>
> ---
>  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)

- Mani

>  }
>  
>  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@...cinc.com>
> 

-- 
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