Re: [PATCH v3] fs: fix unintentional arithmetic wraparound in offset calculation

[Justin Stitt]

Hi,

On Thu, May 16, 2024 at 6:13 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> On Fri, May 17, 2024 at 12:29:06AM +0000, Justin Stitt wrote:
> > When running syzkaller with the newly reintroduced signed integer
> > overflow sanitizer we encounter this report:
>
> why do you keep saying it's unintentional?  it's clearly intended.

Right, "unintentional" is a poor choice of phrasing. I actually mean:
"overflow-checking arithmetic was done in a way that intrinsically
causes an overflow (wraparound)".

I can clearly see the intent of the code; there's even comments saying
exactly what it does: "/* Ensure offsets don't wrap. */"... So the
thinking is: let's use the overflow-checking helpers so we can get a
good signal through the sanitizers on _real_ bugs, especially in spots
with no bounds handling.


Thanks
Justin