[pkg-cryptsetup-devel] Bug#698758: cryptsetup: cryptscripts_start deadlocks for 2 min when run from udev script

[Andrew Stimpson]

Package: cryptsetup
Version: 2:1.4.3-4
Severity: minor
Tags: patch

Dear Maintainer,

I have a LUKS container on a removable drive, and wanted cryptdisks_start
to automatically open it (using the decrypt_derived keyscript) whenever 
I plugged it in.  An obvious way to achieve this is with a udev script.  
However, cryptdisks_start calls 'udevadm settle' at a certain point.  So 
any such udev script will deadlock until the default 120 second timeout 
is reached.  Having to wait 2 minutes for the devices for my encrypted 
USB drive to appear is not really a big deal, but it is annoying.

I propose the following patch to /lib/cryptsetup/cryptdisks.functions 
which checks whether or not the script is being called by a binary 
called '/sbin/udevd' before calling 'udevadm settle'.  This solves my 
problem, yet I feel like there should be a better way to do this by 
playing around with --seq-start or --seq-end option to udevadm.  I don't 
really understand the situation that requires that 'udevadm settle' 
command to be there.  A quick googling indicated that that it's 
important for avoiding a race condition involving the detection of new
swap devices.

### BEGIN PATCH ###

--- a/lib/cryptsetup/cryptdisks.functions
+++ b/lib/cryptsetup/cryptdisks.functions
@@ -430,7 +430,12 @@
 # Rename the device from its temp name to its final name, which will
 # trigger mountall
 finalize_device () {
-	if [ -x /sbin/udevadm ]; then
+	local parent_link
+
+	parent_link="/proc/$PPID/exe"
+	if [ ! -h $parent_link ] || \
+	   [ "$( /bin/readlink $parent_link )" != "/sbin/udevd" ] && \
+	   [ -x /sbin/udevadm ]; then
         	udevadm settle
     	fi
     	dmsetup rename "${dst}_unformatted" "$dst"

### END PATCH ###

-- Package-specific info:
-- /proc/cmdline
BOOT_IMAGE=/vmlinuz-3.2.0-4-amd64 root=UUID=fd750c27-b2d1-4bcc-a6f9-339ebea239a1 ro nouveau.blacklist=1 i915.i915_enable_rc6=1 i915.semaphores=1 pcie_aspm=force quiet

-- System Information:
Debian Release: 7.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.2.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages cryptsetup depends on:
ii  cryptsetup-bin         2:1.4.3-4
ii  debconf [debconf-2.0]  1.5.49
ii  dmsetup                2:1.02.74-4
ii  libc6                  2.13-37

Versions of packages cryptsetup recommends:
ii  busybox                                 1:1.20.0-7
ii  console-setup                           1.88
ii  initramfs-tools [linux-initramfs-tool]  0.109
ii  kbd                                     1.15.3-9

Versions of packages cryptsetup suggests:
ii  dosfstools              3.0.13-1
ii  liblocale-gettext-perl  1.05-7+b1

-- debconf information:
  cryptsetup/prerm_active_mappings: true