bin/80798: mount_portal pipe leaves file descriptors open for child processes

Mateusz Guzik mjguzik at
Sat Jun 9 09:18:51 UTC 2012

On Sat, Jun 09, 2012 at 08:50:06AM +0000, Jukka A. Ukkonen wrote:
>  It seems that item 2 is not a real issue, because the unused
>  stdin is bound to /dev/null exactly as it should be to avoid
>  stdin being accidentally bound to some file while the child
>  program is running.
>  The same /dev/null treatment works also for stdout to avoid
>  accidentally writing to an unexpected file.
>  The stderr is directed to a pipe which in turn gets forwarded
>  to the syslogd.
>  While the item 1 has been an anomaly it has not been a big
>  issue. The only extra fds left for the child program have been
>  a read-only descriptor to /etc/fstab and a writable pipe to
>  feed syslogd.
>  It seems lsof opens its own new file descriptor under /tmp.
>  So, that one does not really count as an anomalous fd.
>  To be really pedantic about the fds to fstab and syslogd
>  apply the attached patch to close everything in the range
>  3...(getdtablesize()-1).
>  Notice, though, that the range may be very large. (Ref.
>  the resource limits.)

Take a look at closefrom(2).

portalfs is rather buggy and not mpsafe (at least not marked as such).
The latter makes it scheduled for removal - see:

With that being said, if you really need portalfs, I would go with
reimplementation from scratch using fuse (perhaps available already).

Mateusz Guzik <mjguzik>

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