[prev in list] [next in list] [prev in thread] [next in thread] 

List:       openssl-dev
Subject:    [openssl.org #2461]
From:       "Michael M. Welch via RT" <rt () openssl ! org>
Date:       2011-02-27 3:18:21
Message-ID: rt-3.4.5-17855-1298776700-1305.2461-6-0 () openssl ! org
[Download RAW message or body]

This transaction appears to have no content

[Attachment #3 (text/html)]

In looking at this further, I note that even in a static lib build of OpenSSL, the \
OPENSSL_cpuid_setup() function is putin the CRT$XCU segment that is to be executed as \
part of static global initializations.&nbsp; Anything that runs like that is subject \
to the same issues as whatever runs in DllMain() is, so this means that this same \
getenv() deadlock problem can also occur even if the OpenSSL library itself is \
static, rather than a DLL.<br /><br /><br />- Michael<br /><br /><br /> <p>On Feb 26, \
2011, <strong>Michael M. Welch</strong> &lt;michael@welch.net&gt; wrote:</p> <div \
class="replyBody"> <blockquote class="email_quote" style="border-left: 2px solid \
#267fdb; margin: 0pt 0pt 0pt 1.8ex; padding-left: 1ex;">Platform:&nbsp; Windows \
only<br />Version:&nbsp; OpenSSL 1.0.0d<br />Source file:&nbsp; crypto\cryptlib.c<br \
/>Function:&nbsp; OPENSSL_cpuid_setup() ( invoked from within DllMain() )<br \
/>Llines:&nbsp; 677 and 678<br />Source:<br />&nbsp;&nbsp;&nbsp; if \
((env=getenv("OPENSSL_ia32cap")))<br />&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; \
OPENSSL_ia32cap_P = strtoul(env,NULL,0)|(1&lt;&lt;10);<br /><br />Problem:<br />Per \
this website ( <a class="parsedLink" \
href="http://msdn.microsoft.com/en-us/library/ms682583%28v=vs.85%29.aspx" \
target="_blank">http://msdn.microsoft.com/en-us/library/ms682583%28v=vs.85%29.aspx</a> \
), Microsoft is on record as stating that calling CRT methods from within DllMain() \
is inherently unsafe and can lead to deadlock situations in multi-threaded \
applications.&nbsp; The example on the given website cautions about getenv() \
specifically.&nbsp; <br /><br />In OpenSSL crypto, the getenv() function is \
explicitly invoked during DllMain(), thus opening up this dangerous situation.&nbsp; \
(Furthermore, it's immediately followed by a call to strtoul(), another CRT \
function.)&nbsp; Deadlocks ensue when one thread runs the DllMain, thus acquiring the \
LoaderLock and then looks to acquire _ENV_LOCK (because getenv() requires that lock), \
but another thread already has _ENV_LOCK and is looking to acquire the LoaderLock.<br \
/><br /><br />- Michael<br /><br /></blockquote> </div>


______________________________________________________________________
OpenSSL Project                                 http://www.openssl.org
Development Mailing List                       openssl-dev@openssl.org
Automated List Manager                           majordomo@openssl.org

[prev in list] [next in list] [prev in thread] [next in thread]