linux/Documentation
Ryan Mallon 312b4e2269 vsprintf: check real user/group id for %pK
Some setuid binaries will allow reading of files which have read
permission by the real user id.  This is problematic with files which
use %pK because the file access permission is checked at open() time,
but the kptr_restrict setting is checked at read() time.  If a setuid
binary opens a %pK file as an unprivileged user, and then elevates
permissions before reading the file, then kernel pointer values may be
leaked.

This happens for example with the setuid pppd application on Ubuntu 12.04:

  $ head -1 /proc/kallsyms
  00000000 T startup_32

  $ pppd file /proc/kallsyms
  pppd: In file /proc/kallsyms: unrecognized option 'c1000000'

This will only leak the pointer value from the first line, but other
setuid binaries may leak more information.

Fix this by adding a check that in addition to the current process having
CAP_SYSLOG, that effective user and group ids are equal to the real ids.
If a setuid binary reads the contents of a file which uses %pK then the
pointer values will be printed as NULL if the real user is unprivileged.

Update the sysctl documentation to reflect the changes, and also correct
the documentation to state the kptr_restrict=0 is the default.

This is a only temporary solution to the issue.  The correct solution is
to do the permission check at open() time on files, and to replace %pK
with a function which checks the open() time permission.  %pK uses in
printk should be removed since no sane permission check can be done, and
instead protected by using dmesg_restrict.

Signed-off-by: Ryan Mallon <rmallon@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Joe Perches <joe@perches.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-11-13 12:09:14 +09:00
..
ABI Staging driver update for 3.13-rc1 2013-11-07 15:07:58 +09:00
DocBook Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-11-12 10:04:41 +09:00
EDID
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RCU rcu: Fix occurrence of "the the" in checklist.txt 2013-09-25 10:07:02 -07:00
accounting
acpi gpiolib / ACPI: document the GPIO descriptor based interface 2013-10-19 23:32:50 +02:00
aoe aoe: remove do-nothing NAME="%k" term from example udev rules 2013-09-11 15:59:28 -07:00
arm Allwinner sunXi SoCs machine additions for 3.13 2013-10-28 10:19:38 -07:00
arm64 arm64: Use 42-bit address space with 64K pages 2013-11-05 17:23:52 +00:00
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extcon extcon: Simplify extcon_dev_register() prototype by removing unnecessary parameter 2013-09-27 09:37:01 +09:00
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firmware_class
fmc doc: Fix typo "is is" in Documentations 2013-08-27 10:50:52 +02:00
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ioctl ALSA: add DICE driver 2013-10-17 21:18:32 +02:00
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kdump
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laptops thinkpad-acpi: Add mute and mic-mute LED functionality 2013-10-17 14:38:44 +02:00
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mips
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mtd doc: Fix typo "is is" in Documentations 2013-08-27 10:50:52 +02:00
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networking doc:net: Fix typo in Documentation/networking 2013-10-30 17:10:20 -04:00
nfc
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power power: Documentation: Update s2ram link 2013-08-27 10:54:52 +02:00
powerpc powerpc: Update the 00-Index in Documentation/powerpc 2013-08-27 14:44:27 +10:00
pps USB: serial: invoke dcd_change ldisc's handler. 2013-09-26 09:45:40 -07:00
prctl
pti
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rapidio
s390 s390/s390dbf: add debug_level_enabled() function 2013-10-24 17:16:53 +02:00
scheduler H8/300 has been dead for several years, the kernel for it has 2013-11-12 14:13:14 +09:00
scsi SCSI misc on 20130915 2013-09-15 17:41:30 -04:00
security
serial serial: core: delete .set_wake() callback 2013-10-16 13:16:19 -07:00
sh
sound ALSA: Fix typo in documentation/alsa 2013-10-29 11:38:04 +01:00
spi
sysctl vsprintf: check real user/group id for %pK 2013-11-13 12:09:14 +09:00
target
thermal thermal: thermal_core: allow binding with limits on bind_params 2013-09-03 09:10:24 -04:00
timers
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trace ftrace, sched: Add TRACE_FLAG_PREEMPT_RESCHED 2013-11-11 12:43:39 +01:00
usb
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virtual Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-09-06 09:36:28 -07:00
vm Documentation/vm/zswap.txt: fix typos 2013-11-13 12:09:05 +09:00
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.gitignore
00-INDEX doc: fix a typo in Documentation/00-INDEX 2013-08-27 10:53:07 +02:00
BUG-HUNTING
Changes
CodingStyle
DMA-API-HOWTO.txt
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DMA-attributes.txt
HOWTO
IPMI.txt
IRQ-affinity.txt
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basic_profiling.txt
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braille-console.txt
bt8xxgpio.txt
btmrvl.txt
bus-virt-phys-mapping.txt
cachetlb.txt
circular-buffers.txt
clk.txt
coccinelle.txt
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cpu-load.txt
cputopology.txt doc: Documentation/cputopology.txt fix typo 2013-09-04 12:59:47 +02:00
crc32.txt
dcdbas.txt
debugging-modules.txt
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dell_rbu.txt
devices.txt
digsig.txt
dma-buf-sharing.txt dma-buf: Expose buffer size to userspace (v2) 2013-09-10 11:36:45 +05:30
dmaengine.txt
dmatest.txt dmatest: make module parameters writable 2013-08-22 22:57:32 -07:00
dontdiff
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edac.txt
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eisa.txt
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gcov.txt
gpio.txt
highuid.txt
hw_random.txt
hwspinlock.txt doc: documentation/hwspinlock.txt fix typo 2013-08-27 10:46:02 +02:00
init.txt
initrd.txt
intel_txt.txt
io-mapping.txt
io_ordering.txt
iostats.txt
irqflags-tracing.txt
isapnp.txt
java.txt
kernel-doc-nano-HOWTO.txt
kernel-docs.txt
kernel-parameters.txt drivers/char/hpet.c: allow user controlled mmap for user processes 2013-11-13 12:09:11 +09:00
kernel-per-CPU-kthreads.txt kthread: Add pointer to vmstat-avoidance patch 2013-09-25 06:49:46 -07:00
kmemcheck.txt Documentation/kmemcheck: update kmemcheck documentation 2013-08-27 10:47:05 +02:00
kmemleak.txt
kobject.txt
kprobes.txt
kref.txt
ldm.txt
local_ops.txt
lockdep-design.txt
lockstat.txt
lockup-watchdogs.txt
logo.gif
logo.txt
magic-number.txt
md.txt
media-framework.txt
memory-barriers.txt
memory-hotplug.txt Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-09-06 09:36:28 -07:00
mono.txt
mutex-design.txt
nommu-mmap.txt
numastat.txt
oops-tracing.txt
padata.txt
parport-lowlevel.txt
parport.txt
percpu-rw-semaphore.txt
phy.txt drivers: phy: add generic PHY framework 2013-09-27 17:35:41 -07:00
pi-futex.txt
pinctrl.txt pinctrl: add documentation for pinctrl_get_group_pins() 2013-10-16 15:35:21 +02:00
pnp.txt
preempt-locking.txt
printk-formats.txt Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-09-06 09:36:28 -07:00
pwm.txt
ramoops.txt
rbtree.txt
remoteproc.txt
rfkill.txt
robust-futex-ABI.txt
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rpmsg.txt
rt-mutex-design.txt
rt-mutex.txt
rtc.txt
serial-console.txt
sgi-ioc4.txt
sgi-visws.txt
smsc_ece1099.txt
sparse.txt
spinlocks.txt
stable_api_nonsense.txt
stable_kernel_rules.txt
static-keys.txt
svga.txt
sysfs-rules.txt
sysrq.txt sysrq: Allow magic SysRq key functions to be disabled through Kconfig 2013-10-16 13:01:44 -07:00
this_cpu_ops.txt
unaligned-memory-access.txt
unicode.txt
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vfio.txt vfio: fix documentation 2013-09-05 16:36:21 -06:00
vgaarbiter.txt
video-output.txt
vme_api.txt
volatile-considered-harmful.txt
workqueue.txt
ww-mutex-design.txt
xz.txt
zorro.txt