DMARC-Filter: OpenDMARC Filter v1.4.2 delorie.com 5678TJDY4117501
Date: Mon, 7 Jul 2025 10:28:14 +0200
To: cygwin@cygwin.com
Subject: Re: Segfault if /proc/PID/maps is opened in parallel threads [CAUSE:
 RtlQueryProcessDebugInformation]
Message-ID: <aGuFHqjgqW51xIFH@calimero.vinschen.de>
Mail-Followup-To: cygwin@cygwin.com
References: <2f7ae08b-80c9-4497-f07c-5d527bbb7ec2@t-online.de>
 <17bba06c-4bdd-01df-8477-235aff98b2cb@t-online.de>
 <9deb7d60-b05d-ad7f-e316-64781687953b@t-online.de>
 <68cbc37b-4825-6e3f-5918-f4fee20d7c05@t-online.de>
 <aGVeI9glhLe2UzTu@calimero.vinschen.de>
 <aGZjZKoT86ptfahW@calimero.vinschen.de>
 <1627d7b2-15f0-c58e-49e1-13f992561bc9@t-online.de>
MIME-Version: 1.0
Content-Disposition: inline
In-Reply-To: <1627d7b2-15f0-c58e-49e1-13f992561bc9@t-online.de>
Precedence: list
From: Corinna Vinschen via Cygwin <cygwin@cygwin.com>
Reply-To: cygwin@cygwin.com
Cc: Corinna Vinschen <corinna-cygwin@cygwin.com>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Errors-To: cygwin-bounces~archive-cygwin=delorie.com@cygwin.com
Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie.com@cygwin.com>

On Jul  5 19:34, Christian Franke via Cygwin wrote:
> Corinna Vinschen via Cygwin wrote:
> > I just added two patches, one of them dropping RtlQueryProcessDebugInformation
> > in favor of EnumProcessModules in dlsym(), the other by adding a global
> > mutex to format_process_maps while accessing the debug buffer.  I could
> > reproduce the crash even if RtlQueryProcessDebugInformation was serialized.
> > I could only avoid the crash by serializing the entire code from
> > RtlCreateQueryDebugBuffer up to and including RtlDestroyQueryDebugBuffer.
> > 
> > This ignores native processes which have a hard time to access
> > /proc anyway.
> 
> Many tests show that the problem with /proc/PID/maps does no longer occur,
> thanks.

Great, thanks for testing.

> dlsym() not tested, sorry.

It's basically a revert of an older patch anyway, since originally
dlsym() used EnumProcessModules().  I checked that it could still
resolve a symbol from cygwin1.dll when using dlsym(RTLD_DEFAULT, ...).


Thanks,
Corinna

-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple