** Description changed:
+ = Summary =
+
+ The version of Upstart in precise is affected by a bug in the way that
+ ".override" [1] file handling is performed.
+
+ If a job has an override file ("/etc/init/*.override") and that override
+ file is deleted before the corresponding job configuration file
+ ("/etc/init/*.conf"), there is a possibility of a crash.
+
+ == Explanation ==
+
+ When a "/etc/init/*.override" file is deleted, Upstart will
+ automatically detect this and reload the corresponding
+ "/etc/init/*.conf" file.
+
+ However, if the ".conf" file (which the ".override" file corresponded
+ to) is deleted at the same time Upstart attempts to read the ".conf"
+ file, an assertion failure could result.
+
+
+ = Code Specifics =
+
+ The erroneous function is "conf_delete_handler()" which is called
+ whenever a file Upstart is watching gets deleted. The end of this
+ function calls conf_reload_path() but although it logs an error message,
+ it does not consume the error object that gets raised when
+ conf_reload_path() fails.
+
+
+ = Affected Releases =
+
+ This bug is only present in precise:
+
+ - Upstart override handling was introduced in Upstart v1.3:
+ - Precise currently uses Upstart 1.5-0ubuntu7.2 (and hence is affected).
+ - Lucid currently uses Upstart 0.6.5-8 (hence, not affected).
+ - Trusty and Vivid use much newer versions of the Upstart which no
+ longer contain the problematic code.
+
+
+ = Fix =
+
+ The fix is simply to have conf_delete_handler() consume the error object
+ (by freeing it) when conf_reload_path() fails.
+
+
+ = Test Case =
+
+ A reliable test case is unfortunately not possible to create, since the
problem comes down to Upstart racing with the deletion of the ".conf"
+ file.
+
+ However, the patch is small and it can be seen that every other failing
+ call to conf_reload_path() free's the resulting error object.
+
+
+ = Regression Potential =
+
+ None expected. The problem is difficult to trigger anwyay and the patch
+ can be seen to correct (what is now) an obvious coding error.
+
+
+ [1] - http://upstart.ubuntu.com/cookbook/#override-file
+
+ = Original Description =
+
ubuntu-touch livefs builds have started killing upstart in the host
system (in this case, precise, although a similar bug appears to be
present in current versions). The livefs build completes, but the host
dies shortly after launchpad-buildd starts trying to remove the build
chroot. The kernel log looks like this:
Mar 10 13:46:55 allspice kernel: [3743880.621603] init:
/home/buildd/build-LIVEFSBUILD-22254/chroot-autobuild/build/chroot/etc/init/tty1.conf:
Unable to reload configuration after override deletion
Mar 10 13:46:55 allspice kernel: [3743880.642455] init: file.c:110: Unhandled
error from nih_file_read: No such file or directory
Mar 10 13:46:55 allspice kernel: [3743880.754281] init: Caught abort, core
dumped
Mar 10 13:46:55 allspice kernel: [3743880.754375] init: file.c:110: Unhandled
error from nih_file_read: No such file or directory
Mar 10 13:46:55 allspice kernel: [3743880.757830] init: Caught abort, core
dumped
This appears to be because a couple of functions call conf_reload_path,
which may leave an nih_error in place if nih_file_read fails, but then
do not dispose of the nih_error. The pattern near the end of
conf_file_visitor (in precise) is probably appropriate.
We're working around this to some extent in livecd-rootfs by removing
the .override files first, but it should never be possible for a chroot
to crash the host's init.
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https://bugs.launchpad.net/bugs/1430403
Title:
ubuntu-touch livefs builds kill upstart in host
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