[Bug libc/9939] New: MCheck is not thread safe - can report false errors on multi threaded apps

[Bug libc/9939] New: MCheck is not thread safe - can report false errors on multi threaded apps

[wdtj at yahoo dot com]

MCheck is not thread safe - can report false errors on multi threaded apps.  

mcheck.c uses the __malloc_hook (et al) feature of malloc.c & arena.c to
intercept memory requests.  During it's processing, it swaps the _hooks back to
their original values and recursively calls the memory request in order to do
the actual memory request.  While this hook is swapped out, another thread could
call the memory request and at that point get memory that bypassed mcheck.  This
memory will then be reported as corrupt if it is freed with the mcheck hook back
in place.

Possible fixes:
1) Add linkage to malloc.c's _int_malloc (el al) functions that would allow
mcheck to access the memory allocation without having to go through the code
implementing the hooks.

2) Change or add a new hook set that allows the hooker to wrapper the call, not
just intercept it.

3) Write a separate memory pool routine for use in mcheck.  (yuck).

-- 
           Summary: MCheck is not thread safe - can report false errors on
                    multi threaded apps
           Product: glibc
           Version: 2.4
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: wdtj at yahoo dot com
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=9939

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[Bug libc/9939] MCheck is not thread safe - can report false errors on multi threaded apps

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2009-03-11 15:14 -------
This is by design.  This can never be changed without breaking various ABIs.

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


http://sourceware.org/bugzilla/show_bug.cgi?id=9939

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[Bug libc/9939] MCheck is not thread safe - can report false errors on multi threaded apps

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=9939

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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[Bug libc/9939] MCheck is not thread safe - can report false errors on multi threaded apps

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=9939

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jan.kratochvil at redhat
                   |                            |dot com

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