[Dovecot] Small problem with src/lib/mountpoint.c

[Mike Brudenell]

Greetings -

Whilst playing with getting quotas from NFS-mounted filestores I've  
just discovered a slight problem with src/lib/mountpoint.c

I had things working on a Solaris 10 test machine which had the  
mailstore mounted 'normally' using an entry in /etc/vfstab.

However when I changed to use the automounter for the mailstore  
obtaining the quota broke.

The problem lies with mountpoint_get().  On a 'normally' mounted  
filestore this obtains the device_path of the remote filestore in the  
form

     remoteservername.some.domain:/remote/path

However when the mailstore was automounted I was instead getting back

     auto_direct

which is the name of the automounter map we're using.

The /etc/mnttab file has TWO entries for the auto-mounted filestore,  
like this:

auto_direct     /mailstore/messages/p   autofs   
direct,ignore,dev=4740014       1184648400
crypt2.york.ac.uk:/vol/vol9/p   /mailstore/messages/p   nfs      
proto=tcp,xattr,dev=4700386     1184668792

Although there are two entries they have different device numbers.   
The mountpoint_get() function attempts to guard against this by  
checking the device number obtained matches that of the path being  
located.

However for some reason I don't understand when getmntent() returns  
the FIRST of the above two entries it supplies the device number of  
the SECOND.  Thus the device numbers match in the mountpoint_get()  
test and it thinks it has found the correct entry.  This leads to the  
device_path being set to the map name -- auto_direct -- instead of  
the host:/path

My fix is to add an additional fstype for the test to ignore:  
"autofs".  The loop skips over any such mounts (along with the  
existing tests for "swap" and "ignore").

I'm attaching my minimal patch in case it's of help to anyone else.

(Timo: would it be possible to get this added into the distribution  
code if you agree it's right?)

Cheers,
Mike Brudenell

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