[Bug 1000802] New: DNS race condition

[bugzilla-daemon at ecoscentric dot com]

http://bugs.ecos.sourceware.org/show_bug.cgi?id=1000802

           Summary: DNS race condition
           Product: eCos
           Version: CVS
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: normal
         Component: TCP/IP
        AssignedTo: gary@mlbassoc.com
        ReportedBy: will_lentz@trimble.com
         QAContact: ecos-bugs@ecos.sourceware.org
             Class: ---


Created an attachment (id=762)
 --> (http://bugs.ecos.sourceware.org/attachment.cgi?id=762)
Fix for DNS race condition

Hi,

There's a race condition in packages/net/ns/dns/current/include/dns_impl.inl
and dns.c.

Here's a quick example of how the current code may cause a problem:
 1) Call cyg_dns_res_start() in thread #1.
    Assume the connect() call blocks for a few seconds.
    Note that at this point 's' is valid, but 'ptdindex' in uninitialized or
invalid.
 2) While thread #1 is blocked, call gethostbyname() (or gethostbyaddr()) in
thread #2.
    The call to free_stored_hent() assumes 'ptdindex' is valid, but it is not.
    If you have asserts on, cyg_thread_get_data(ptdindex) will hit an assert or
return a bogus pointer value that may get passed to free().

The attached fix:
 - puts 's' and free_stored_hent()/ptdindex inside the mutex lock so they are
   always consistent with each other.
 - makes 'init' file-visible so it can protect against accessing an
uninitialized mutex.

Thanks,
Will


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