Re: mount options noexec,nosuid,nodev

[Paul Goyette <paul%whooppee.com@localhost>]

Here's an example from my current machine - kernel and userland built from 
sources dated 2016-02-16 at 03:01:55 UTC

*** initial conditions from system boot ***

#  uname -r
7.99.26
# df
Filesystem    1K-blocks       Used      Avail %Cap Mounted on
/dev/wd0a      50829066    9345322   38942292  19% /
/dev/wd0e      51615924     481204   48553924   0% /var
/dev/wd0f      51610146    1593252   47436388   3% /home
/dev/wd0g     245273624   66196776  166813168  28% /build
kernfs                1          1          0 100% /kern
ptyfs                 1          1          0 100% /dev/pts
procfs                4          4          0 100% /proc
tmpfs           2064480     196620    1867860   9% /var/shm
# grep build /etc/fstab
/dev/wd0g       /build          ffs     rw,log         1     2
# cd /build
# ls -l /build/TEST.sh
-rwxr-xr-x  1 root  staff  30 Apr  4 06:26 TEST.sh
# cat /build/TEST.sh
#! /bin/sh

echo "This is $0"

*** The boot-time mount worked, and the various flags were set

# /build/TEST.sh
This is /build/TEST.sh

*** So, unmount, and remount on the running system

# umount /build
# mount /build
#  df
Filesystem    1K-blocks       Used      Avail %Cap Mounted on
/dev/wd0a      50829066    9345322   38942292  19% /
/dev/wd0e      51615924     481304   48553824   0% /var
/dev/wd0f      51610146    1593254   47436386   3% /home
kernfs                1          1          0 100% /kern
ptyfs                 1          1          0 100% /dev/pts
procfs                4          4          0 100% /proc
tmpfs           2064480     196620    1867860   9% /var/shm
/dev/wd0g     245273624   66196780  166813164  28% /build

*** The flags were cleared on the remount!

# /build/TEST.sh
/build/TEST.sh: Permission denied.

*** Just to make sure, unmount and then remount with explicit flags set

# umount /build
# mount -o exec,suid,dev /build
# /build/TEST.sh
This is /build/TEST.sh
#

*** Yup, it works again.




> On 26 Mar 2016 11:20 pm, "Paul Goyette" <paul%whooppee.com@localhost> wrote:
>
> > I always seem to get bitten by this!
> >
> > I had a power-outage yesterday, and at restart I disabled one of my
> > filesystems in /etc/fstab (since a fsck of this fs takes a rather long
> > time).  After the reboot, I manually ran fsck and then mounted the
> > filesystem with
> >
> >         mount /myfs
> >
> > Yes, I forgot to specify "-o exec,suid,dev" so I couldn't execute any
> > scripts (or other executables).
> >
> > But looking through the manual pages, there doesn't seem to be any
> > indication on when "-o noexec,nosuid,nodev" becomes the default!  (It seems
> > not to be the default when mount is invoked during /etc/rc.d startup
> > processing, but only after the system is up.)
> >
> > Where is this documented?  And perhaps the mount(8) man page might benefit
> > if these options included an appropriate cross-ref?
> >
> >
> >
> > +------------------+--------------------------+------------------------+
> > | Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:      |
> > | (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com   |
> > | Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd.org |
> > +------------------+--------------------------+------------------------+
>
>
> !DSPAM:57011e098692117718468!

+------------------+--------------------------+------------------------+
| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:      |
| (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com   |
| Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd.org |
+------------------+--------------------------+------------------------+