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NFSv4 callback processes linger on kernel 4.11.5


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I use 5.32 dev on NanoPi NEO:

$ uname -a
Linux watchdev 4.11.5-sun8i #11 SMP Fri Jun 23 20:03:23 CEST 2017 armv7l GNU/Linux

I use NFSv4 and autofs. The number of "[NFSv4 callback]" processes increase each time a volume is mounted, and does not decrease when un-mounting:

# ps axwww |grep -i nfsv4 | grep -v grep
 1478 ?        S      0:00 [NFSv4 callback]
 1501 ?        S      0:00 [NFSv4 callback]
 1515 ?        S      0:00 [NFSv4 callback]
# umount /storage/motion
# ps axwww |grep -i nfsv4 | grep -v grep
 1478 ?        S      0:00 [NFSv4 callback]
 1501 ?        S      0:00 [NFSv4 callback]
 1515 ?        S      0:00 [NFSv4 callback]
# ls /storage/motion
backup	config	firmware  public  scripts  videos
# ps axwww |grep -i nfsv4 | grep -v grep
 1478 ?        S      0:00 [NFSv4 callback]
 1501 ?        S      0:00 [NFSv4 callback]
 1515 ?        S      0:00 [NFSv4 callback]
 1550 ?        S      0:00 [NFSv4 callback]
# umount /storage/motion
# ps axwww |grep -i nfsv4 | grep -v grep
 1478 ?        S      0:00 [NFSv4 callback]
 1501 ?        S      0:00 [NFSv4 callback]
 1515 ?        S      0:00 [NFSv4 callback]
 1550 ?        S      0:00 [NFSv4 callback]
# ls /storage/motion
backup	config	firmware  public  scripts  videos
# ps axwww |grep -i nfsv4 | grep -v grep
 1478 ?        S      0:00 [NFSv4 callback]
 1501 ?        S      0:00 [NFSv4 callback]
 1515 ?        S      0:00 [NFSv4 callback]
 1550 ?        S      0:00 [NFSv4 callback]
 1566 ?        S      0:00 [NFSv4 callback]

This causes me problems because I use my NanoPi NEO boards as home-made IP cameras (motion software) and motion events are stored on a PS server running Debian. This causes autofs to un-mount and re-mount the file server's volume many times a day.

 

After searching a bit, I found several references to this issue, and it seems that the problem was introduced in 4.9 and that a fix is available in 4.11.6:

https://security-tracker.debian.org/tracker/CVE-2017-9059

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=863550

 

Is there any plan to upgrade the Armbian kernel to 4.11.6?

 

Thanks.

Pascal.

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For now, I have decided to play with the autofs timeout option (making it really long). Since my server is always on, and there is only one NFS share, I have no issue if it remains mounted for a long time..

 

(I use autofs because it nicely handles the power outage cases, i.e. the system automatically recovers from a power outage and resumes operations with no manual intervention.)

 

Hopefully a long timeout will workaround the leakage by avoiding umount operations (best case), or at least reducing them to a handful per day (worst case). Then I can wait for the kernel upgrade. Lazy me..

 

Thanks for the quick answer.

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