linux-kernel - Re: [PATCH] objtool: check: give big enough buffer for pv

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Date:   Fri, 14 Jan 2022 09:53:07 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sergei Trofimovich <slyich@...il.com>
Cc:     linux-kernel@...r.kernel.org, Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH] objtool: check: give big enough buffer for pv_ops

On Fri, Jan 14, 2022 at 07:57:56AM +0000, Sergei Trofimovich wrote:
> On gcc-12 build fails flagging possible buffer overflow:
> 
>     check.c: In function 'validate_call':
>     check.c:2865:58: error: '%d' directive output may be truncated writing between 1 and 10 bytes into a region of size 9 [-Werror=format-truncation=]
>      2865 |                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
>           |                                                          ^~
> 
> I think it's a valid warning:
> 
>     static char pvname[16];
>     int idx;
>     ...
>     idx = (rel->addend / sizeof(void *));
>     snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
> 
> we have only 7 chars for %d while it could take up to 9.

Right, very unlikely to have that many pv_ops, but it doesn't hurt to
fix this.

Thanks!