linux/drivers
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
..
accessibility
acpi x86, ACPI, mm: Revert movablemem_map support 2013-03-02 09:34:39 -08:00
amba Merge branch 'for-linus' of git://git.linaro.org/people/rmk/linux-arm 2013-03-03 11:54:39 -08:00
ata 1) apply, and then revert, the sysfs export of ATA host controller number. 2013-02-24 17:32:15 -08:00
atm hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
auxdisplay
base CHROMIUM: dma-buf: restore args on failure of dma_buf_mmap 2013-02-27 15:14:02 +05:30
bcma Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless 2013-02-14 14:23:33 -05:00
block Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2013-02-28 17:43:09 -08:00
bluetooth Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-02-21 17:40:58 -08:00
bus
cdrom
char drivers/char/misc.c:misc_register(): do not loop on misc_list unconditionally 2013-02-27 19:10:21 -08:00
clk hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
clocksource ImgTec Meta architecture changes for v3.9-rc1 2013-03-03 12:06:09 -08:00
connector net: proc: change proc_net_remove to remove_proc_entry 2013-02-18 14:53:08 -05:00
cpufreq ACPI and power management fixes for 3.9-rc1 2013-02-25 21:25:17 -08:00
cpuidle arm-soc: soc-specific updates 2013-02-21 15:27:22 -08:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2013-02-25 15:56:15 -08:00
dca dca: convert to idr_alloc() 2013-02-27 19:10:15 -08:00
devfreq
dio
dma Merge branch 'next' of git://git.infradead.org/users/vkoul/slave-dma 2013-03-03 10:20:22 -08:00
edac Merge branch 'linux_next' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-edac 2013-02-28 20:42:33 -08:00
eisa
extcon Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
firewire firewire: convert to idr_alloc() 2013-02-27 19:10:15 -08:00
firmware fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
gpio gpio: convert to idr_alloc() 2013-02-27 19:10:15 -08:00
gpu hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
hid Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
hsi hsi: fix kernel-doc warnings 2013-03-01 13:39:00 -08:00
hv Drivers: hv: vmbus: Use the new infrastructure for delivering VMBUS interrupts 2013-02-27 10:15:53 -08:00
hwmon ACPI and power management updates for 3.9-rc1 2013-02-20 11:26:56 -08:00
hwspinlock
i2c idr: remove MAX_IDR_MASK and move left MAX_IDR_* into idr.c 2013-02-27 19:10:20 -08:00
ide Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
idle Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-22 19:25:09 -08:00
iio Staging tree update for 3.9-rc1 2013-02-21 12:11:44 -08:00
infiniband fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
input Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2013-03-03 12:58:43 -08:00
iommu Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
ipack Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
irqchip ImgTec Meta architecture changes for v3.9-rc1 2013-03-03 12:06:09 -08:00
isdn hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
leds Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/cooloney/linux-leds 2013-02-26 09:29:02 -08:00
lguest All trivial, thanks to the stuff which didn't quite make it time. 2013-02-26 14:49:12 -08:00
macintosh Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2013-02-23 17:09:55 -08:00
mailbox
md dm cache: add cleaner policy 2013-03-01 22:45:52 +00:00
media arm-soc: late OMAP changes 2013-02-28 20:00:40 -08:00
memory
memstick memstick: move the dereference below the NULL test 2013-02-27 19:10:23 -08:00
message
mfd mfd: convert to idr_alloc() 2013-02-27 19:10:17 -08:00
misc fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
mmc Merge branches 'devel-stable', 'fixes' and 'mmci' into for-linus 2013-03-03 00:32:50 +00:00
mtd fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
net Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2013-03-02 07:44:16 -08:00
nfc Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next into for-davem 2013-02-18 13:47:13 -05:00
ntb
nubus
of Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-02-21 17:40:58 -08:00
oprofile fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
parisc Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
parport Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2013-02-21 17:54:03 -08:00
pci hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
pcmcia Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-02-21 17:40:58 -08:00
pinctrl arm-soc: device tree conversions 2013-02-21 15:38:49 -08:00
platform Merge branch 'for_linus' of git://cavan.codon.org.uk/platform-drivers-x86 2013-03-03 10:16:19 -08:00
pnp Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
power power: convert to idr_alloc() 2013-02-27 19:10:18 -08:00
pps drivers/pps/clients/pps-gpio.c: use devm_kzalloc 2013-02-27 19:10:23 -08:00
ps3
ptp
pwm pwm: Changes for v3.9-rc1 2013-02-26 09:34:29 -08:00
rapidio
regulator Merge remote-tracking branch 'regulator/topic/tps65090' into regulator-next 2013-02-19 12:43:12 +00:00
remoteproc remoteproc: convert to idr_alloc() 2013-02-27 19:10:18 -08:00
rpmsg rpmsg: convert to idr_alloc() 2013-02-27 19:10:18 -08:00
rtc rtc: stmp3xxx: add wdt-accessor function 2013-03-01 12:40:36 +01:00
s390 qdio: remove unused parameters 2013-02-28 09:37:12 +01:00
sbus Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-02-26 20:16:07 -08:00
scsi SCSI for-linus on 20130301 2013-03-02 11:42:16 -08:00
sfi
sh
sn
spi arm-soc: soc-specific updates 2013-02-21 15:27:22 -08:00
ssb Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into mips-for-linux-next 2013-02-22 10:07:30 +01:00
staging fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
target Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2013-03-02 11:43:27 -08:00
tc
thermal Fix mis-merge of intel_powerclamp.c resulting in compile error 2013-02-28 20:23:09 -08:00
tty Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2013-03-03 13:23:03 -08:00
uio uio: convert to idr_alloc() 2013-02-27 19:10:19 -08:00
usb fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
uwb
vfio vfio: convert to idr_alloc() 2013-02-27 19:10:19 -08:00
vhost Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2013-02-26 11:42:23 -08:00
video backlight: add new lp8788 backlight driver 2013-02-27 19:10:09 -08:00
virt
virtio All trivial, thanks to the stuff which didn't quite make it time. 2013-02-26 14:49:12 -08:00
vlynq
vme vme: add missing put_device() after device_register() fails 2013-02-14 09:24:14 -08:00
w1 arm-soc: i.MX DT changes 2013-02-28 19:59:34 -08:00
watchdog watchdog: sp805_wdt depends on ARM 2013-03-01 12:56:26 +01:00
xen fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
zorro new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
Kconfig Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
Makefile Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2013-02-23 17:09:55 -08:00