Re: [PATCH] hw/dma: prevent overflow in soc_dma_set_request

[Peter Maydell]

On Tue, 9 Apr 2024 at 12:54, Anastasia Belova <abelova@astralinux.ru> wrote:
>
> ch->num can reach values up to 31. Add casting to
> a larger type before performing left shift to
> prevent integer overflow.

If ch->num can only reach up to 31, then 1 << ch->num
is fine, because QEMU can assume that integers are 32 bits,
and we compile with -fwrapv so there isn't a problem with
shifting into the sign bit.

And I agree that we shouldn't ever have a ch->num greater
than 31, because the worst case here is when we call
soc_dma_init() with an argument of 32, which sets up
soc_dma_ch_s structs with values of num from 0 to 31.

So this doesn't seem to me to be fixing an active bug.
Am I missing something?

thanks
-- PMM