> On Mar 27, 2023, at 4:16 PM, Bjorn Andersson <quic_bjorande@xxxxxxxxxxx> wrote:
>
> On Sun, Mar 26, 2023 at 11:52:23AM -0500, Alex Elder wrote:
>> In gsi_trans_pool_init_dma(), the total size of a pool of memory
>> used for DMA transactions is calculated. However the calculation is
>> done incorrectly.
>>
>> For 4KB pages, this total size is currently always more than one
>> page, and as a result, the calculation produces a positive (though
>> incorrect) total size. The code still works in this case; we just
>> end up with fewer DMA pool entries than we intended.
>>
>> Bjorn Andersson tested booting a kernel with 16KB pages, and hit a
>> null pointer derereference in sg_alloc_append_table_from_pages(),
>> descending from gsi_trans_pool_init_dma(). The cause of this was
>> that a 16KB total size was going to be allocated, and with 16KB
>> pages the order of that allocation is 0. The total_size calculation
>> yielded 0, which eventually led to the crash.
>>
>> Correcting the total_size calculation fixes the problem.
>>
>> Reported-by: <quic_bjorande@xxxxxxxxxxx>
>> Tested-by: <quic_bjorande@xxxxxxxxxxx>
>
> It would be nice to add "Bjorn Andersson" to these two.
>
Oh yeah sorry about that. I’ll add it. -Alex
> Regards,
> Bjorn
>
>> Fixes: 9dd441e4ed57 ("soc: qcom: ipa: GSI transactions")
>> Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
>> ---
>> drivers/net/ipa/gsi_trans.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ipa/gsi_trans.c b/drivers/net/ipa/gsi_trans.c
>> index 0f52c068c46d6..ee6fb00b71eb6 100644
>> --- a/drivers/net/ipa/gsi_trans.c
>> +++ b/drivers/net/ipa/gsi_trans.c
>> @@ -156,7 +156,7 @@ int gsi_trans_pool_init_dma(struct device *dev, struct gsi_trans_pool *pool,
>> * gsi_trans_pool_exit_dma() can assume the total allocated
>> * size is exactly (count * size).
>> */
>> - total_size = get_order(total_size) << PAGE_SHIFT;
>> + total_size = PAGE_SIZE << get_order(total_size);
>>
>> virt = dma_alloc_coherent(dev, total_size, &addr, GFP_KERNEL);
>> if (!virt)
>> --
>> 2.34.1
>>
