Re: [PATCH] io_uring: cast id to u64 before shifting in io_allocate_rbuf_ring()

[Pavel Begunkov]

On 3/16/26 19:37, Jens Axboe wrote:
> On 3/16/26 9:06 AM, Anas Iqbal wrote:
> > Smatch warns:
> > io_uring/zcrx.c:393 io_allocate_rbuf_ring() warn: should 'id << 16' be a 64 bit type?
> >
> > The expression 'id << IORING_OFF_PBUF_SHIFT' is evaluated using 32-bit
> > arithmetic because id is a u32. This may overflow before being promoted
> > to the 64-bit mmap_offset.
> >
> > Cast id to u64 before shifting to ensure the shift is performed in
> > 64-bit arithmetic.
>
> I'd be impressed if 'id' could be large enough to cause this to
> overflow. AFAICT, you'd need more than 64K interface queues registered
> to hit this. So I think this should be reframed as a cleanup, to appease
> smatch.

Pretty much so. I'll queue up the patch targeting 7.1, thanks

--
Pavel Begunkov