[Bug 285658] [PATCH] SIGFPE in /usr/bin/primes

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=285658

            Bug ID: 285658
           Summary: [PATCH] SIGFPE in /usr/bin/primes
           Product: Base System
           Version: 13.5-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: bin
          Assignee: bugs@FreeBSD.org
          Reporter: mfp49_freebsd@plass-family.net

Created attachment 259027
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=259027&action=edit
Fix crash in /usr/bin/primes

Here is one example:

$ /usr/bin/primes 5000000000 5000000099
Floating point exception
$ 

I tracked down the problem to the do-while loop in src/usr.bin/primes/primes.c,
which can run beyond the end of the primes[] array when fact_lim >= *pr_limit;
in my case the fetched value is zero, leading to an integer divide-by-zero.

This bug appears to be quite old. Possibly it has been masked by the
presence of non-zero memory after the primes array.

A patch (against CURRENT) is attached.

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