Bug 1465735 - non root user run kdumpctl cause dead loop
Summary: non root user run kdumpctl cause dead loop
Keywords:
Status: CLOSED RAWHIDE
Alias: None
Product: Fedora
Classification: Fedora
Component: kexec-tools
Version: rawhide
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: ---
Assignee: Ziyue Yang
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2017-06-28 04:57 UTC by Dave Young
Modified: 2017-07-24 04:34 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
: 1474174 (view as bug list)
Environment:
Last Closed: 2017-07-14 08:11:15 UTC


Attachments (Terms of Use)

Description Dave Young 2017-06-28 04:57:19 UTC
Description of problem:
Run `kdumpctl status` as normal user, get below error messages:

Another app is currently holding the kdump lock; waiting for it to exit...
flock: 9: Bad file descriptor
Another app is currently holding the kdump lock; waiting for it to exit...
flock: 9: Bad file descriptor
Another app is currently holding the kdump lock; waiting for it to exit...
flock: 9: Bad file descriptor
Another app is currently holding the kdump lock; waiting for it to exit...
flock: 9: Bad file descriptor
Another app is currently holding the kdump lock; waiting for it to exit...
flock: 9: Bad file descriptor
Another app is currently holding the kdump lock; waiting for it to exit...
flock: 9: Bad file descriptor
Another app is currently holding the kdump lock; waiting for it to exit...
flock: 9: Bad file descriptor
Another app is currently holding the kdump lock; waiting for it to exit...
flock: 9: Bad file descriptor
Another app is currently holding the kdump lock; waiting for it to exit..

Version-Release number of selected component (if applicable):


How reproducible:


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Additional info:

Comment 1 Ziyue Yang 2017-07-03 07:43:23 UTC
This bug is caused by behavior difference between bash and sh(bash in posix).

In the function single_instance_lock in kdumpctl script, there is

exec 9>/var/lock/kdump

which will fail in user mode. However, this fail will cause script exit under bash and non-exit under sh, causing infinite loop because the flock will always fail.

According to the 15th item in
ftp://ftp.gnu.org/old-gnu/Manuals/bash-2.02/html_node/bashref_66.html

If a POSIX.2 special builtin returns an error status, a non-interactive shell exits.

And according to
https://www.gnu.org/software/bash/manual/html_node/Special-Builtins.html

These are the POSIX special builtins:

break : . continue eval exec exit export readonly return set
shift trap unset

I suggest fixing the bug by checking exec return value.

Comment 2 Ziyue Yang 2017-07-03 07:43:50 UTC
Sorry it should be the 16th item.


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