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

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Date:   Wed, 1 Nov 2023 10:50:22 +0530
From:   Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To:     Manivannan Sadhasivam <mani@...nel.org>
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 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@...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

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@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>
>>