Hi Geert, Christoph,
Thank you for your comments!
> From: Geert Uytterhoeven, Sent: Friday, June 14, 2019 4:27 PM
>
> Hi Christoph,
>
> On Fri, Jun 14, 2019 at 9:18 AM Christoph Hellwig wrote:
> > On Thu, Jun 13, 2019 at 10:35:44PM +0200, Geert Uytterhoeven wrote:
> > > I'm always triggered by the use of min_t() and other casts:
> > > mmc->max_blk_size and mmc->max_blk_count are both unsigned int.
> > > dma_max_mapping_size() returns size_t, which can be 64-bit.
> > >
> > > 1) Can the multiplication overflow?
> > > Probably not, as per commit 2a55c1eac7882232 ("mmc: renesas_sdhi:
> > > prevent overflow for max_req_size"), but I thought I'd better ask.
Geert-san:
I agree.
> > > 2) In theory, dma_max_mapping_size() can return a number that doesn't
> > > fit in 32-bit, and will be truncated (to e.g. 0), leading to max_req_size
> > > is zero?
Geert-san:
I agree. If dma_max_mapping_size() return 0x1_0000_0000, it will be truncated to 0
and then max_req_size is set to zero. It is a problem. Also, the second argument
"mmc->max_blk_size * mmc->max_blk_count" will not be overflow and then the value is
0xffff_ffff or less. So, I also think this should use size_t instead of unsigned int.
> > This really should use a min_t on size_t. Otherwise the patch looks
> > fine:
>
> Followed by another min() to make it fit in mmc->max_req_size, which is
> unsigned int.
Geert-san:
I'm afraid, but I cannot understand this means.
Is this patch is possible to be upstream? Or, do you have any concern?
Best regards,
Yoshihiro Shimoda
