Re: [PATCH] apply: use strcmp(3) for comparing strings in gitdiff_verify_name()

From: René Scharfe <l.s.r@web.de>
Date: Jul 8, 2017, 11:43 UTC
Message-ID: <e46a7de9-3e0e-4eeb-c9a3-a8b5f22620b4@web.de>
In-Reply-To: <87tw2ngp94.fsf@linux-m68k.org>

Am 08.07.2017 um 13:08 schrieb Andreas Schwab:

Show 8 quoted lines

> On Jul 08 2017, René Scharfe <l.s.r@web.de> wrote:
> 
>> Avoid running over the end of another -- a C string whose length we
>> don't know -- by using strcmp(3) instead of memcmp(3) for comparing it
>> with another C string.
> 
> That's not a good justification for the change, since memcmp never reads
> past the differing characters.

Interesting.  Where does that guarantee come from?

ASan reports an overflow with the following test program for me on Debian testing x64:

#include <string.h>

int main(int argc, char **argv)
{
         char a[32] = "1234567890123456789012345678901";
         char b[2] = "a";
         return memcmp(a, b, 32);
}