openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 137 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-rc b/Documentation/ABI/testing/sysfs-class-rc
new file mode 100644
index 000000000..84e46d70d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rc
@@ -0,0 +1,137 @@
+What:		/sys/class/rc/
+Date:		Apr 2010
+KernelVersion:	2.6.35
+Contact:	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
+Description:
+		The rc/ class sub-directory belongs to the Remote Controller
+		core and provides a sysfs interface for configuring infrared
+		remote controller receivers.
+
+What:		/sys/class/rc/rc<N>/
+Date:		Apr 2010
+KernelVersion:	2.6.35
+Contact:	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
+Description:
+		A /sys/class/rc/rcN directory is created for each remote
+		control receiver device where N is the number of the receiver.
+
+What:		/sys/class/rc/rc<N>/protocols
+Date:		Jun 2010
+KernelVersion:	2.6.36
+Contact:	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
+Description:
+		Reading this file returns a list of available protocols,
+		something like::
+
+		    "rc5 [rc6] nec jvc [sony]"
+
+		Enabled protocols are shown in [] brackets.
+
+		Writing "+proto" will add a protocol to the list of enabled
+		protocols.
+
+		Writing "-proto" will remove a protocol from the list of enabled
+		protocols.
+
+		Writing "proto" will enable only "proto".
+
+		Writing "none" will disable all protocols.
+
+		Write fails with EINVAL if an invalid protocol combination or
+		unknown protocol name is used.
+
+What:		/sys/class/rc/rc<N>/filter
+Date:		Jan 2014
+KernelVersion:	3.15
+Contact:	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
+Description:
+		Sets the scancode filter expected value.
+
+		Use in combination with /sys/class/rc/rcN/filter_mask to set the
+		expected value of the bits set in the filter mask.
+		If the hardware supports it then scancodes which do not match
+		the filter will be ignored. Otherwise the write will fail with
+		an error.
+
+		This value may be reset to 0 if the current protocol is altered.
+
+What:		/sys/class/rc/rc<N>/filter_mask
+Date:		Jan 2014
+KernelVersion:	3.15
+Contact:	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
+Description:
+		Sets the scancode filter mask of bits to compare.
+		Use in combination with /sys/class/rc/rcN/filter to set the bits
+		of the scancode which should be compared against the expected
+		value. A value of 0 disables the filter to allow all valid
+		scancodes to be processed.
+
+		If the hardware supports it then scancodes which do not match
+		the filter will be ignored. Otherwise the write will fail with
+		an error.
+
+		This value may be reset to 0 if the current protocol is altered.
+
+What:		/sys/class/rc/rc<N>/wakeup_protocols
+Date:		Feb 2017
+KernelVersion:	4.11
+Contact:	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
+Description:
+		Reading this file returns a list of available protocols to use
+		for the wakeup filter, something like::
+
+		    "rc-5 nec nec-x rc-6-0 rc-6-6a-24 [rc-6-6a-32] rc-6-mce"
+
+		Note that protocol variants are listed, so "nec", "sony",
+		"rc-5", "rc-6" have their different bit length encodings
+		listed if available.
+
+		The enabled wakeup protocol is shown in [] brackets.
+
+		Only one protocol can be selected at a time.
+
+		Writing "proto" will use "proto" for wakeup events.
+
+		Writing "none" will disable wakeup.
+
+		Write fails with EINVAL if an invalid protocol combination or
+		unknown protocol name is used, or if wakeup is not supported by
+		the hardware.
+
+What:		/sys/class/rc/rc<N>/wakeup_filter
+Date:		Jan 2014
+KernelVersion:	3.15
+Contact:	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
+Description:
+		Sets the scancode wakeup filter expected value.
+
+		Use in combination with /sys/class/rc/rcN/wakeup_filter_mask to
+		set the expected value of the bits set in the wakeup filter mask
+		to trigger a system wake event.
+
+		If the hardware supports it and wakeup_filter_mask is not 0 then
+		scancodes which match the filter will wake the system from e.g.
+		suspend to RAM or power off.
+
+		Otherwise the write will fail with an error.
+
+		This value may be reset to 0 if the wakeup protocol is altered.
+
+What:		/sys/class/rc/rc<N>/wakeup_filter_mask
+Date:		Jan 2014
+KernelVersion:	3.15
+Contact:	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
+Description:
+		Sets the scancode wakeup filter mask of bits to compare.
+
+		Use in combination with /sys/class/rc/rcN/wakeup_filter to set
+		the bits of the scancode which should be compared against the
+		expected value to trigger a system wake event.
+
+		If the hardware supports it and wakeup_filter_mask is not 0 then
+		scancodes which match the filter will wake the system from e.g.
+		suspend to RAM or power off.
+
+		Otherwise the write will fail with an error.
+
+		This value may be reset to 0 if the wakeup protocol is altered.