[Bug libc/17439] New: Conditional jump or move depends on uninitialised value(s)

[Bug libc/17439] New: Conditional jump or move depends on uninitialised value(s)

[libm3l at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17439

            Bug ID: 17439
           Summary: Conditional jump or move depends on uninitialised
                    value(s)
           Product: glibc
           Version: 2.19
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: libm3l at gmail dot com
                CC: drepper.fsp at gmail dot com

Created attachment 7810
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7810&action=edit
source of test program

Hello

I have an Conditional jump or move depends on uninitialised value(s) from
valgrind:

valgrind --tool=memcheck  --trace-children=yes
--vex-iropt-register-updates=allregs-at-mem-access --leak-check=full
--leak-resolution=high --show-reachable=yes  --track-origins=yes ./a.out

The output is:

==21572== Memcheck, a memory error detector
==21572== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==21572== Using Valgrind-3.9.0 and LibVEX; rerun with -h for copyright info
==21572== Command: ./a.out
==21572== 
==21572== Conditional jump or move depends on uninitialised value(s)
==21572==    at 0x4017C04: index (in /lib64/ld-2.19.so)
==21572==    by 0x4007502: expand_dynamic_string_token (in /lib64/ld-2.19.so)
==21572==    by 0x4008164: _dl_map_object (in /lib64/ld-2.19.so)
==21572==    by 0x40015DD: map_doit (in /lib64/ld-2.19.so)
==21572==    by 0x400E9FF: _dl_catch_error (in /lib64/ld-2.19.so)
==21572==    by 0x4000FE7: do_preload (in /lib64/ld-2.19.so)
==21572==    by 0x40037B6: dl_main (in /lib64/ld-2.19.so)
==21572==    by 0x4015397: _dl_sysdep_start (in /lib64/ld-2.19.so)
==21572==    by 0x4004C84: _dl_start (in /lib64/ld-2.19.so)
==21572==    by 0x40013F7: ??? (in /lib64/ld-2.19.so)
==21572==  Uninitialised value was created by a stack allocation
==21572==    at 0x4003740: dl_main (in /lib64/ld-2.19.so)
==21572== 
==21572== 
==21572== HEAP SUMMARY:
==21572==     in use at exit: 0 bytes in 0 blocks
==21572==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==21572== 
==21572== All heap blocks were freed -- no leaks are possible
==21572== 
==21572== For counts of detected and suppressed errors, rerun with: -v
==21572== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)



Here is output of  /lib/libc.so.6 
GNU C Library (Gentoo 2.19-r1 p3) stable release version 2.19, by Roland
McGrath et al.
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.7.3.
Compiled on a Linux 3.13.0 system on 2014-09-27.
Available extensions:
        C stubs add-on version 2.1.2
        crypt add-on version 2.1 by Michael Glad and others
        GNU Libidn by Simon Josefsson
        Native POSIX Threads Library by Ulrich Drepper et al
        BIND-8.2.3-T5B
libc ABIs: UNIQUE IFUNC
For bug reporting instructions, please see:
<http://bugs.gentoo.org/>.


Output of  uname -a
Linux localhost 3.17.0-rc6+ #1 SMP Wed Sep 24 04:55:21 MDT 2014 x86_64 Intel(R)
Core(TM) i7-4700MQ CPU @ 2.40GHz GenuineIntel GNU/Linux


Attached is a short code I used for testing

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[Bug libc/17439] Conditional jump or move depends on uninitialised value(s)

[libm3l at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17439

Adam Jirasek <libm3l at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |libm3l at gmail dot com

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[Bug libc/17439] Conditional jump or move depends on uninitialised value(s)

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=17439

Andreas Schwab <schwab@linux-m68k.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Andreas Schwab <schwab@linux-m68k.org> ---
This is a false positive, strchr is reading in 8 byte chunks as long as it
doesn't cross a page boundary.  You need to rebuild valgrind to enable the
built-in suppressions.

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[Bug libc/17439] Conditional jump or move depends on uninitialised value(s)

[libm3l at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17439

--- Comment #2 from Adam Jirasek <libm3l at gmail dot com> ---
(In reply to Andreas Schwab from comment #1)
> This is a false positive, strchr is reading in 8 byte chunks as long as it
> doesn't cross a page boundary.  You need to rebuild valgrind to enable the
> built-in suppressions.

Thanks!

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