[Bug 1883025] [NEW] [focal SRU] davfs2 unable to unmount: segfault error 4 in libc.so

Launchpad Bug Tracker 1883025 at bugs.launchpad.net
Sun Apr 4 13:50:10 UTC 2021

You have been subscribed to a public bug by Rolf Leggewie (r0lf):


umount.davfs consistently segfault in focal.  This leads to a number of
medium severity issues.

- inability to unmount (this might have security implications)
- inability to remount
- autofs fails to unmount
- reports of higher load in multi-user environments
- computer "hangs" on shutdown waiting for successful umount completion


No need for a specific test case, simply mount a resource via
davfs2.mount.  Calling umount.davfs2 on that mount in focal will result
in a segfault every time.  Exit code 255 and failure is recorded in
syslog.  The mount stays mounted.

To verify the fix from #2 which is the backport of the fix from
upstream, simply recompile davfs2 and try the procedure once more to see
if the problem has been solved.


I will leave this mostly to others to evaluate.  Currently,
umount.davfs2 is completely dysfunctional so it's hard to imagine a
regression for a binary that isn't doing anything except segfaulting.


groovy and later versions have already been fixed via a new upstream
release.  Upstream discussion of the a and m mixup can be found at the
links below.


I am getting segfaults everytime I want to unmount my webdav online-
space (segfault error 4).

Hardware failure is impossible as I see - because error already reported on project page (and fixed).
Error should be fixed in davfs 1.5.6 (Maybe easiest to bump to version 1.5.6 on ubuntu repos ?) :)

See (line 4-6):

See 2:

EDIT: Using Ubuntu 20.04 x64

** Affects: davfs2 (Ubuntu)
     Importance: Undecided
         Status: Confirmed

** Tags: davfs focal patch segfault unmount
[focal SRU] davfs2 unable to unmount: segfault error 4 in libc.so
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