linux/drivers/staging
Eric W. Biederman 7f78e03513 fs: Limit sys_mount to only request filesystem modules.
Modify the request_module to prefix the file system type with "fs-"
and add aliases to all of the filesystems that can be built as modules
to match.

A common practice is to build all of the kernel code and leave code
that is not commonly needed as modules, with the result that many
users are exposed to any bug anywhere in the kernel.

Looking for filesystems with a fs- prefix limits the pool of possible
modules that can be loaded by mount to just filesystems trivially
making things safer with no real cost.

Using aliases means user space can control the policy of which
filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf
with blacklist and alias directives.  Allowing simple, safe,
well understood work-arounds to known problematic software.

This also addresses a rare but unfortunate problem where the filesystem
name is not the same as it's module name and module auto-loading
would not work.  While writing this patch I saw a handful of such
cases.  The most significant being autofs that lives in the module
autofs4.

This is relevant to user namespaces because we can reach the request
module in get_fs_type() without having any special permissions, and
people get uncomfortable when a user specified string (in this case
the filesystem type) goes all of the way to request_module.

After having looked at this issue I don't think there is any
particular reason to perform any filtering or permission checks beyond
making it clear in the module request that we want a filesystem
module.  The common pattern in the kernel is to call request_module()
without regards to the users permissions.  In general all a filesystem
module does once loaded is call register_filesystem() and go to sleep.
Which means there is not much attack surface exposed by loading a
filesytem module unless the filesystem is mounted.  In a user
namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT,
which most filesystems do not set today.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Kees Cook <keescook@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-03-03 19:36:31 -08:00
..
android hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
asus_oled staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
bcm Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
ccg fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
ced1401 staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
comedi more file_inode() open-coded instances 2013-02-27 16:59:05 -05:00
cptm1217 staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
crystalhd staging: crystalhd: remove use of __devexit 2012-11-21 15:05:12 -08:00
csr Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
cxt1e1 staging: cxt1e1: buffer overflow in do_del_chan() 2013-01-25 11:21:26 -08:00
dgrp Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
echo staging: echo.c: fix memory leakage 2013-01-07 14:03:32 -08:00
et131x Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
frontier staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
ft1000 Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
fwserial tty/serial patches for 3.9-rc1 2013-02-21 13:41:04 -08:00
gdm72xx staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
goldfish staging/goldfish: Add MTD dependency to KCONFIG 2013-02-07 17:16:07 -08:00
iio Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
imx-drm staging: ipu-di: Change DI address info to dev_dbg 2013-01-17 13:52:37 -08:00
keucr staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
line6 staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
media [media] staging: media: Remove unnecessary OOM messages 2013-02-13 17:32:46 -02:00
net staging: net: remove use of __devexit 2012-11-21 15:05:02 -08:00
nvec arm-soc: soc-specific updates 2013-02-21 15:27:22 -08:00
octeon Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-02-21 17:40:58 -08:00
olpc_dcon staging: olpc_dcon: remove use of __devexit_p 2012-11-21 15:05:00 -08:00
omap-thermal Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
ozwpan staging/ozwpan: Mark read only parameters and structs as const 2013-02-15 15:14:30 -08:00
panel staging/panel: Mark local functions/structs static and add const if applicable (fix sparse warnings) 2013-02-15 10:20:14 -08:00
phison
quickstart ACPI: Remove useless type argument of driver .remove() operation 2013-01-26 00:37:24 +01:00
rtl8187se staging/rtl8187se: Mark functions as static to silence sparse 2013-02-15 10:28:37 -08:00
rtl8192e Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-01-15 15:05:59 -05:00
rtl8192u staging/rtl8192u/ieee80211: Fix buffer overflow in ieee80211_softmac_wx.c 2013-02-14 09:26:23 -08:00
rtl8712 rtl8712: remove unused definitions from ethernet.h 2013-01-11 16:39:12 -08:00
rts5139
sb105x tty/serial patches for 3.9-rc1 2013-02-21 13:41:04 -08:00
sbe-2t3e3 staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
sep staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
serqt_usb2 TTY: switch tty_schedule_flip 2013-01-15 22:43:15 -08:00
silicom
slicoss staging: slicoss: Fix space-related checkpatch.pl warnings 2013-01-17 13:53:06 -08:00
sm7xxfb staging: sm7xxfb: remove use of __devexit 2012-11-21 15:05:12 -08:00
speakup tty/serial patches for 3.9-rc1 2013-02-21 13:41:04 -08:00
ste_rmi4 staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
tidspbridge arm-soc: multiplatform support 2013-02-21 15:20:41 -08:00
usbip Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
vme Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
vt6655 staging: vt6655: no braces needed for single statement if , for blocks 2013-01-17 13:17:03 -08:00
vt6656 staging: vt6656: replaced custom TRUE definition with true 2013-02-15 10:48:24 -08:00
winbond staging: Add angle bracket before and after the URL 2013-01-07 14:56:04 -08:00
wlags49_h2 Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
wlags49_h25
wlan-ng Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
xgifb staging/xgifb: Remove duplicated code in loops. 2013-02-15 15:12:40 -08:00
zcache mm: rename page struct field helpers 2013-02-23 17:50:18 -08:00
zram staging: Remove unnecessary OOM messages 2013-02-11 10:10:33 -08:00
zsmalloc mm: rename page struct field helpers 2013-02-23 17:50:18 -08:00
Kconfig Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux 2013-02-25 16:46:44 -08:00
Makefile Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux 2013-02-25 16:46:44 -08:00
staging.c