Bug 689471

Summary: SSE4 strncmp failure
Product: Red Hat Enterprise Linux 6 Reporter: Andreas Schwab <schwab>
Component: glibcAssignee: Andreas Schwab <schwab>
Status: CLOSED ERRATA QA Contact: qe-baseos-tools-bugs
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 6.0CC: fweimer, mfranc, pmuller
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: glibc-2.12-1.24.el6 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2011-05-19 13:16:28 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Andreas Schwab 2011-03-21 15:59:44 UTC 
H.J. Lu      2011-03-21 05:42:34 CET  
On Intel Core i7, I got

[hjl@gnu-6 997]$ cat saved.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>

int main()
{
    char *buf, *buf2;

    buf = (char*)mmap((void*)0x100000000, 0x2000 * 2,
                      PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    buf = mmap((char *)buf, 0x2000, PROT_READ | PROT_WRITE,
               MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
    memset(buf, 'a', 0x2000);
    buf[0x1fff] = 0;
    buf2 = strdup(buf);
    if (strncmp (buf + 3994, buf2 + 2635, 6241) >= 0)
      abort ();

    return 0;
}
[hjl@gnu-6 997]$ gcc saved.c
[hjl@gnu-6 997]$ ./a.out 
Segmentation fault
[hjl@gnu-6 997]$ gdb a.out 
GNU gdb (GDB) 7.2.50.20110312-cvs
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /export/home/hjl/bugs/libc/997/a.out...(no debugging
symbols found)...done.
(gdb) r
Starting program: /export/home/hjl/bugs/libc/997/a.out 

Program received signal SIGSEGV, Segmentation fault.
0x0000003f7d3214a0 in __strncmp_sse42 () from /lib64/libc.so.6
(gdb)
Comment 4 errata-xmlrpc 2011-05-19 13:16:28 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2011-0584.html