Bug 986390 - Bind mounting onto /proc/NNN/YYY leaves a stale, non-removeable entry in the mount table when the process exits [NEEDINFO]
Bind mounting onto /proc/NNN/YYY leaves a stale, non-removeable entry in the ...
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
Unspecified Unspecified
unspecified Severity unspecified
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Assigned To: Kernel Maintainer List
Fedora Extras Quality Assurance
Depends On:
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Reported: 2013-07-19 12:15 EDT by Daniel Berrange
Modified: 2014-03-10 10:41 EDT (History)
5 users (show)

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2014-03-10 10:41:29 EDT
Type: Bug
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---
jwboyer: needinfo?

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Description Daniel Berrange 2013-07-19 12:15:21 EDT
Description of problem:
Due to some foolishness on my part, I was attempting to bind mount a file onto /proc/self/cgroup, instead of /proc/THE-ACTUAL-PID/cgroup. I noticed that when I do this, I get a stale, non-removeable entry in the kernel mount table.

# cp /proc/self/cgroup  /root/cgroup

# mount --bind /root/cgroup /proc/self/cgroup 

# grep proc /proc/mounts 
proc /proc proc rw,relatime 0 0
systemd-1 /proc/sys/fs/binfmt_misc autofs rw,relatime,fd=33,pgrp=1,timeout=300,minproto=5,maxproto=5,direct 0 0
binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw,relatime 0 0
sunrpc /proc/fs/nfsd nfsd rw,relatime 0 0
/dev/mapper/vg_t500wlan-lv_root /proc/26770/cgroup ext4 rw,seclabel,relatime,data=ordered 0 0

# umount -f /proc/26770/cgroup
umount: /proc/26770/cgroup: not found

In fact if I use /proc/1234/cgroup, i'll hit the same problem when process 1234 exits.

So the kernel doesn't appear to cleanup bind mounts under any /proc/NNNNN/ location when the process NNNN exits.

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

How reproducible:

Steps to Reproduce:
1. Bind mount a file onto /proc/NNNN/YYYY, where NNN is any process ID, or 'self'
2. Let the process NNN exit
3. Look for the mount bind

Actual results:
The bind mount still exists & cannot be removed, since /proc/NNN no longer exists

Expected results:
Any mounts under /proc/NNNN are purged when process NNN exits.

Additional info:
Comment 1 Josh Boyer 2013-09-18 16:45:04 EDT
*********** MASS BUG UPDATE **************

We apologize for the inconvenience.  There is a large number of bugs to go through and several of them have gone stale.  Due to this, we are doing a mass bug update across all of the Fedora 19 kernel bugs.

Fedora 19 has now been rebased to 3.11.1-200.fc19.  Please test this kernel update and let us know if you issue has been resolved or if it is still present with the newer kernel.

If you experience different issues, please open a new bug report for those.
Comment 2 Justin M. Forbes 2014-03-10 10:41:29 EDT
*********** MASS BUG UPDATE **************

This bug has been in a needinfo state for more than 1 month and is being closed with insufficient data due to inactivity. If this is still an issue with Fedora 19, please feel free to reopen the bug and provide the additional information requested.

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