Re: CPPCheck found 24 high risk bugs in Git v.1.8.3.4

[Jeff King <peff@peff.net>]

On Tue, Aug 20, 2013 at 01:15:02AM +0200, Erik Faye-Lund wrote:

> This one seems real, although it's quite theoretical. It should only happen
> in cases where the log-message contains "%1", the initial malloc passed and
> reallocing two more bytes failed.
> 
> However, what's much more of a disaster: "pos" is used after the call to
> realloc might have moved the memory!

Yeah, agreed on both counts.

> I guess something like this should fix both issues. Sorry about the
> lack of indentation, it seems Gmail has regressed, and the old compose
> mode is somehow gone... (also sorry for triple-posting to some of you,
> Gmail seems particularly broken today)
> 
> diff --git a/compat/win32/syslog.c b/compat/win32/syslog.c
> index d015e43..0641f4e 100644
> --- a/compat/win32/syslog.c
> +++ b/compat/win32/syslog.c
> @@ -43,11 +43,14 @@ void syslog(int priority, const char *fmt, ...)
>   va_end(ap);
> 
>   while ((pos = strstr(str, "%1")) != NULL) {
> - str = realloc(str, ++str_len + 1);
> - if (!str) {
> + char *tmp = realloc(str, ++str_len + 1);
> + if (!tmp) {
>   warning("realloc failed: '%s'", strerror(errno));
> + free(str);
>   return;
>   }
> + pos = tmp + (pos - str);
> + str = tmp;
>   memmove(pos + 2, pos + 1, strlen(pos));
>   pos[1] = ' ';
>   }

Yes, that looks like the right solution. You could also convert "pos" to
an integer index rather than a pointer (but then you end up adding it it
to the pointer in the memmove call, which is probably just as ugly).

-Peff