Re: [PATCH net v3] net: ipa: compute DMA pool size properly

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On Tue, Mar 28, 2023 at 11:27:51AM -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: Bjorn Andersson <quic_bjorande@xxxxxxxxxxx>
> Tested-by: Bjorn Andersson <quic_bjorande@xxxxxxxxxxx>
> Fixes: 9dd441e4ed57 ("soc: qcom: ipa: GSI transactions")
> Reviewed-by: Mark Bloch <mbloch@xxxxxxxxxx>
> Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
> ---
> Note: This was reported via private communication.
> v3: - Added Mark Bloch's reviewed-by tag.
> v2: - Added Bjorn's actual name to tags.  
>  drivers/net/ipa/gsi_trans.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Leon Romanovsky <leonro@xxxxxxxxxx>

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