Messages in this thread | | | From | Bill Wendling <> | Date | Thu, 9 Jun 2022 15:49:21 -0700 | Subject | Re: [PATCH 00/12] Clang -Wformat warning fixes |
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On Thu, Jun 9, 2022 at 3:25 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Thu, 9 Jun 2022 22:16:19 +0000 Bill Wendling <morbo@google.com> wrote: > > > This patch set fixes some clang warnings when -Wformat is enabled. > > > > tldr: > > - printk(msg); > + printk("%s", msg); > > the only reason to make this change is where `msg' could contain a `%'. > Generally, it came from userspace.
It helps kernel developers not accidentally to insert an unescaped '%' in their messages, potentially exposing their code to an attack vector.
> Otherwise these changes are a > useless consumer of runtime resources.
Calling a "printf" style function is already insanely expensive. :-) I understand that it's not okay blithely to increase runtime resources simply because it's already slow, but in this case it's worthwhile.
> I think it would be better to quieten clang in some fashion.
The "printk" and similar functions all have the "__printf" attribute. I don't know of a modification to that attribute which can turn off this type of check.
-bw
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