linux-kernel - Re: [RFC PATCH 0/7] runtime format string checking

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Date:   Mon, 5 Nov 2018 10:33:44 +0100
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Kees Cook <keescook@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/7] runtime format string checking

On 2018-11-01 23:57, Kees Cook wrote:

>> Yes, gcc should be able to infer the constness of drv from the fact that
>> it's never assigned to elsewhere in the function... I think I saw that
>> on some gcc todo list at some point.
> 
> If you find that bug, I'll add it to my gcc bug tracking list. :P

I looked into doing it myself (just for the format checking case, not
for variables in general), but gave up after a few hours. So I created
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87879 . I tried adding you
to the cc list, but it seems you don't have a gcc bugzilla account (?).

Looking more into this, as you can see above, it's actually a little
worse than "false positive" -Wformat-nonliteral - see the f2() case.

[At https://godbolt.org/z/KC4ZRK I also included the const char[] case,
which works as the const char* const case wrt. format checking, but for
some reason gcc open-codes the strlen(). But that's a separate issue,
and not one we should care about, since the const char[] thing is wrong
regardless due to the bade code gen]

Rasmus