bin/181154: snprintf with out of bounds positional arguments results in segfault

[Garrett Cooper]

>Number:         181154
>Category:       bin
>Synopsis:       snprintf with out of bounds positional arguments results in segfault
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Aug 09 01:00:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Garrett Cooper
>Release:        10-CURRENT
>Organization:
EMC Isilon
>Environment:
>Description:
The following piece of test code...

ATF_TC(snprintf_posarg_error);
ATF_TC_HEAD(snprintf_posarg_error, tc)
{

        atf_tc_set_md_var(tc, "descr", "test for positional arguments out "
            "of bounds");
}

ATF_TC_BODY(snprintf_posarg_error, tc)
{
        char s[16], fmt[32];

        snprintf(fmt, sizeof(fmt), "%%%zu$d", SIZE_MAX / sizeof(size_t));

        ATF_CHECK(snprintf(s, sizeof(s), fmt, -23) == -1);
}

Produces this segfault:

tc-start: 1376007948.899132, snprintf_posarg_error
tc-se:Test program crashed; attempting to get stack trace
tc-se:Core was generated by `t_printf'.
tc-se:Program terminated with signal 11, Segmentation fault.
tc-se:#0  0x28186bc3 in vfprintf () from /lib/libc.so.7
tc-se:Stack trace complete
tc-end: 1376007948.947316, snprintf_posarg_error, failed, Test program received signal 11 (core dumped)
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: