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

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Message-ID: <20231101051748.GD2897@thinkpad>
Date:   Wed, 1 Nov 2023 10:47:48 +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, stable@...r.kernel.org
Subject: Re: [PATCH v2] bus: mhi: host: Add alignment check for event ring
 read pointer

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@...r.kernel.org
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@...cinc.com>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

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

> ---
> 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@quicinc.com
> ---
>  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@...cinc.com>
> 

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