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, 97 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-mce b/Documentation/ABI/testing/sysfs-mce
new file mode 100644
index 000000000..83172f50e
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-mce
@@ -0,0 +1,97 @@
+What:		/sys/devices/system/machinecheck/machinecheckX/
+Contact:	Andi Kleen <ak@linux.intel.com>
+Date:		Feb, 2007
+Description:
+		(X = CPU number)
+
+		Machine checks report internal hardware error conditions
+		detected by the CPU. Uncorrected errors typically cause a
+		machine check (often with panic), corrected ones cause a
+		machine check log entry.
+
+		For more details about the x86 machine check architecture
+		see the Intel and AMD architecture manuals from their
+		developer websites.
+
+		For more details about the architecture
+		see http://one.firstfloor.org/~andi/mce.pdf
+
+		Each CPU has its own directory.
+
+What:		/sys/devices/system/machinecheck/machinecheckX/bank<Y>
+Contact:	Andi Kleen <ak@linux.intel.com>
+Date:		Feb, 2007
+Description:
+		(Y bank number)
+
+		64bit Hex bitmask enabling/disabling specific subevents for
+		bank Y.
+
+		When a bit in the bitmask is zero then the respective
+		subevent will not be reported.
+
+		By default all events are enabled.
+
+		Note that BIOS maintain another mask to disable specific events
+		per bank.  This is not visible here
+
+What:		/sys/devices/system/machinecheck/machinecheckX/check_interval
+Contact:	Andi Kleen <ak@linux.intel.com>
+Date:		Feb, 2007
+Description:
+		The entries appear for each CPU, but they are truly shared
+		between all CPUs.
+
+		How often to poll for corrected machine check errors, in
+		seconds (Note output is hexadecimal). Default 5 minutes.
+		When the poller finds MCEs it triggers an exponential speedup
+		(poll more often) on the polling interval.  When the poller
+		stops finding MCEs, it triggers an exponential backoff
+		(poll less often) on the polling interval. The check_interval
+		variable is both the initial and maximum polling interval.
+		0 means no polling for corrected machine check errors
+		(but some corrected errors might be still reported
+		in other ways)
+
+What:		/sys/devices/system/machinecheck/machinecheckX/trigger
+Contact:	Andi Kleen <ak@linux.intel.com>
+Date:		Feb, 2007
+Description:
+		The entries appear for each CPU, but they are truly shared
+		between all CPUs.
+
+		Program to run when a machine check event is detected.
+		This is an alternative to running mcelog regularly from cron
+		and allows to detect events faster.
+
+What:		/sys/devices/system/machinecheck/machinecheckX/monarch_timeout
+Contact:	Andi Kleen <ak@linux.intel.com>
+Date:		Feb, 2007
+Description:
+		How long to wait for the other CPUs to machine check too on a
+		exception. 0 to disable waiting for other CPUs.
+
+		Unit: us
+
+What:		/sys/devices/system/machinecheck/machinecheckX/ignore_ce
+Contact:	Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
+Date:		Jun 2009
+Description:
+		Disables polling and CMCI for corrected errors.
+		All corrected events are not cleared and kept in bank MSRs.
+
+What:		/sys/devices/system/machinecheck/machinecheckX/dont_log_ce
+Contact:	Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
+Date:		Jun 2009
+Description:
+		Disables logging for corrected errors.
+		All reported corrected errors will be cleared silently.
+
+		This option will be useful if you never care about corrected
+		errors.
+
+What:		/sys/devices/system/machinecheck/machinecheckX/cmci_disabled
+Contact:	Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
+Date:		Jun 2009
+Description:
+		Disables the CMCI feature.