Re: UBSAN report for main [so: 14] /usr/bin/whatis: non-zero (48) and zero offsets from null pointer in qsort.c

On 2022-Jan-11, at 05:19, Stefan Esser <se@freebsd.org> wrote:

> Am 11.01.22 um 08:40 schrieb Mark Millard:
>> # whatis dog
>> /usr/main-src/lib/libc/stdlib/qsort.c:114:23: runtime error: applying non-zero offset 48 to null pointer
>> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/main-src/lib/libc/stdlib/qsort.c:114:23 in 
>> /usr/main-src/lib/libc/stdlib/qsort.c:114:44: runtime error: applying zero offset to null pointer
>> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/main-src/lib/libc/stdlib/qsort.c:114:44 in 
>> whatis: nothing appropriate
>> 
>> This seems to be only for the not-found case.
>> 
>> ===
>> Mark Millard
>> marklmi at yahoo.com
> 
> The undefined behavior is caused by insufficient checking of parameters
> in mansearch.c.
> 
> As part of the initializations performed at the start of mansearch(),
> the variables cur and *res are initialized to 0 resp. NULL:
> 
> 	cur = maxres = 0;	
> 	if (res != NULL)
> 		*res = NULL;
> 
> If no match is found, these values are unchanged at line 223, where res
> is checked to be non-NULL, but then *res is passed to qsort() and that
> is still NULL.
> 
> Suggested fix (also attached to avoid white-space issues):
> 
> --- usr.bin/mandoc/mansearch.c
> +++ usr.bin/mandoc/mansearch.c
> @@ -220,7 +220,7 @@
> 	if (cur && search->firstmatch)
> 		break;
> 	}
> -	if (res != NULL)
> +	if (res != NULL && *res != NULL)
> 		qsort(*res, cur, sizeof(struct manpage), manpage_compare);
> 	if (chdir_status && getcwd_status && chdir(buf) == -1)
> 		warn("%s", buf);
> 
> (File name as in OpenBSD, it is contrib/mandoc/mansearch.c in FreeBSD.)

Cool. Thanks.

(But I'm not a committer so someone else
will have to deal with doing an update to
the file in git --and likely MFC'ing it.)

===
Mark Millard
marklmi at yahoo.com