From: Peter Ross <Peter.Ross(at)>
Date: Tue, 9 Sep 2008 14:03:30 +1000 (EST)


ich habe mich gerade durch den Security Advice
II. Problem Description

Various user defined input such as mount points, devices, and mount
options are prepared and passed as arguments to nmount(2) into the
kernel. Under certain error conditions, user defined data will be
copied into a stack allocated buffer stored in the kernel without
sufficient bounds checking.
IV. Workaround

It is possible to work around this issue by allowing only privileged
users to mount file systems by running the following sysctl(8)

# sysctl vfs.usermount=0

V. Solution

NOTE WELL: Even with this fix allowing users to mount arbitrary media
should not be considered safe. Most of the file systems in FreeBSD
was not built to protect safeguard against malicious devices. While
such bugs in file systems are fixed when found, a complete audit has
not been perfomed on the file system code.
Klar, soweit.

Trotzdem, es kann sehr nützlich sein, für ein Desktopsystem z.B.,
unpriviligierte Mounts z.B. von USB-Devices möglich zu machen.

Wenn ich die Optionen in /etc/fstab vordefiniere, kann keiner mit den
Optionen rumspielen.

Wäre es sinnvoll und machbar, einen solchen Sicherheitslevel "zwischen
vfs.usermount=0 und vfs.usermount=1" zu implementieren?

Es grüßt

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Received on Tue 09 Sep 2008 - 06:05:02 CEST

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