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Bug 614573 - fprintd blocks screen unlock
fprintd blocks screen unlock
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: fprintd (Show other bugs)
All Linux
low Severity medium
: rc
: ---
Assigned To: Bastien Nocera
: 613970 (view as bug list)
Depends On:
  Show dependency treegraph
Reported: 2010-07-14 15:11 EDT by Dan Williams
Modified: 2010-11-10 15:24 EST (History)
8 users (show)

See Also:
Fixed In Version: fprintd-0.1-19.git04fd09cfa.el6
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2010-11-10 15:24:18 EST
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
screensaver log from launch until password timeout (14.47 KB, text/plain)
2010-07-14 15:36 EDT, Dan Williams
no flags Details
log from 2.28.3-5.el6 with *works* (10.82 KB, text/plain)
2010-07-14 15:45 EDT, Dan Williams
no flags Details

  None (edit)
Description Dan Williams 2010-07-14 15:11:10 EDT
fprintd appears to block unlocking the screen when it's locked via inactivity or via Ctl+Alt+L.  I'm able to log in using my password, but after locking the screen I'm unable to unlock it.

gnome-screensaver takes my password and hangs in "Checking..." until it times the auth attempt out.  I know the password is correct.

I can work around the issue by commenting out the:

auth sufficient pam_fprintd.so

line in my /etc/pam.d/system-auth file.  I can *also* work around the issue by moving the /usr/share/dbus-1/system-services/net.reactivated.Fprint.service file to prevent fprintd from loading.

I have not enrolled any fingerprints on my system, and this is an up-to-date install of RHEL6 as of 2010-07-14.
Comment 2 Dan Williams 2010-07-14 15:36:17 EDT
Created attachment 431885 [details]
screensaver log from launch until password timeout
Comment 3 Dan Williams 2010-07-14 15:40:56 EDT
Comment 4 Dan Williams 2010-07-14 15:45:44 EDT
Created attachment 431886 [details]
log from 2.28.3-5.el6 with *works*
Comment 5 Dan Williams 2010-07-14 15:47:51 EDT
So downgrading to gnome-screensaver-2.28.3-5.el6 makes things work again.
Comment 6 Dan Williams 2010-07-14 16:03:06 EDT
THe problem appears to be caused by patch #14, remove-theme-support.patch.  Builds without that patch do not exhibit the hang.
Comment 7 Ray Strode [halfline] 2010-07-15 16:46:53 EDT
can't unlock screen is a serious blocker, devack+
Comment 8 Ray Strode [halfline] 2010-07-27 09:56:17 EDT
I spent some time trying to reproduce this yesterday and came up short.  I also read through the patch and can't come up with anything immediately plausible.

We can always revert the patch I guess, but I'd like to avoid that if possible.

Roderick, any chance you could set up a test user that I could remotely debug with?
Comment 9 Ray Strode [halfline] 2010-07-27 18:20:41 EDT
So Roderick McCloud (Dan Williams) set up vnc on his machine and I was able to reproduce.  It took several hours for me to figure out the problem, but it turns out to be an issue in pam_fprintd. 

pam_fprintd is very careful to use its own main loop context (as it should) to prevent getting in the way of the gnome-screensaver.

Unfortunately, there's a small bug in its logic where it ends up removing a random file descriptor from the default context.  In Dan's case that file descriptor is really important.  It's what tells gnome-screensaver when to drop the dialog.

The patch is as simple as:

-			g_source_remove (timeout_id);
+			g_source_destroy (source);

(g_source_remove always operates on the default context)

marking MODIFIED
Comment 11 Ray Strode [halfline] 2010-07-29 09:54:09 EDT
*** Bug 613970 has been marked as a duplicate of this bug. ***
Comment 12 Vladimir Benes 2010-08-04 08:50:05 EDT
cannot see this error any more in snapshot 9
Comment 13 releng-rhel@redhat.com 2010-11-10 15:24:18 EST
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.

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