WSL2-Linux-Kernel/drivers/misc
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
..
altera-stapl Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media 2011-10-31 15:42:54 -07:00
c2port misc/c2port: convert to idr_alloc() 2013-02-27 19:10:17 -08:00
carma dmaengine: remove dma_async_memcpy_pending() macro 2013-01-07 22:05:09 -08:00
cb710 drivers/misc/cb710: add missing GENERIC_HARDIRQS dependency 2013-02-08 12:23:53 -08:00
eeprom drivers: misc: at24: mention other supported types in Kconfig 2013-01-28 05:26:41 +01:00
ibmasm fs: Limit sys_mount to only request filesystem modules. 2013-03-03 19:36:31 -08:00
lis3lv02d misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
mei mei: fix undefined wd symbols when MEI_ME is not set 2013-02-07 14:00:25 -08:00
sgi-gru hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
sgi-xp SGI-XP: handle non-fatal traps 2012-12-20 17:40:20 -08:00
ti-st Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
vmw_vmci hlist: drop the node parameter from iterators 2013-02-27 19:10:24 -08:00
Kconfig Char/Misc driver patches for 3.9-rc1 2013-02-21 13:57:13 -08:00
Makefile misc: Add Lattice ECP3 FPGA configuration via SPI 2013-01-17 10:25:03 -08:00
ad525x_dpot-i2c.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
ad525x_dpot-spi.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
ad525x_dpot.c misc: remove use of __devinit 2012-11-21 12:51:53 -08:00
ad525x_dpot.h Merge branch 'char-misc-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc 2012-01-09 12:08:59 -08:00
apds990x.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
apds9802als.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
arm-charlcd.c tree-wide: fix comment/printk typos 2010-11-01 15:38:34 -04:00
atmel-ssc.c Driver core patches for 3.9-rc1 2013-02-21 12:05:51 -08:00
atmel_pwm.c treewide: Convert uses of struct resource to resource_size(ptr) 2011-06-10 14:55:36 +02:00
atmel_tclib.c ARM: at91/tc/clocksource: Add 32 bit variant to Timer Counter 2012-03-01 13:38:49 +01:00
bh1770glc.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
bh1780gli.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
bmp085-i2c.c misc: remove use of __devinit 2012-11-21 12:51:53 -08:00
bmp085-spi.c misc: remove use of __devinit 2012-11-21 12:51:53 -08:00
bmp085.c misc: remove use of __devinit 2012-11-21 12:51:53 -08:00
bmp085.h misc: add support for bmp18x chips to the bmp085 driver 2012-04-18 14:57:14 -07:00
cs5535-mfgpt.c misc: remove use of __devinit 2012-11-21 12:51:53 -08:00
ds1682.c MISC: convert drivers/misc/* to use module_i2c_driver() 2012-01-24 16:31:49 -08:00
enclosure.c [SCSI] enclosure: fix error path - actually return ERR_PTR() on error 2010-07-27 12:03:48 -05:00
ep93xx_pwm.c drivers/misc/ep93xx_pwm.c: world-writable sysfs files 2011-03-22 17:44:11 -07:00
fsa9480.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
hmc6352.c MISC: convert drivers/misc/* to use module_i2c_driver() 2012-01-24 16:31:49 -08:00
hpilo.c misc: remove use of __devinit 2012-11-21 12:51:53 -08:00
hpilo.h misc: hpilo: increase number of max supported channels 2012-06-14 17:22:12 -07:00
ics932s401.c MISC: convert drivers/misc/* to use module_i2c_driver() 2012-01-24 16:31:49 -08:00
ioc4.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
isl29003.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
isl29020.c MISC: convert drivers/misc/* to use module_i2c_driver() 2012-01-24 16:31:49 -08:00
kgdbts.c kgdb/kgdbts: support ppc64 2013-03-02 08:52:17 -06:00
lattice-ecp3-config.c misc: lattice-ecp3-config.c: remove __dev* markings 2013-01-17 10:25:26 -08:00
lkdtm.c drivers/misc/lkdtm.c: fix missing allocation failure check 2012-07-30 17:25:22 -07:00
pch_phub.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
phantom.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
pti.c TTY/Serial merge for 3.8-rc1 2012-12-11 14:08:47 -08:00
spear13xx_pcie_gadget.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
ti_dac7512.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
tifm_7xx1.c tifm: use module_pci_driver 2012-09-05 14:10:29 -07:00
tifm_core.c misc/tifm_core: convert to idr_alloc() 2013-02-27 19:10:17 -08:00
tsl2550.c misc: remove use of __devexit 2012-11-21 12:53:32 -08:00
vmw_balloon.c vmw_balloon: fix for a -Wuninitialized warning 2012-02-02 16:28:13 -08:00