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, 13 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-amd-pmf b/Documentation/ABI/testing/sysfs-amd-pmf
new file mode 100644
index 000000000..7fc0e1c2b
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-amd-pmf
@@ -0,0 +1,13 @@
+What:		/sys/devices/platform/*/cnqf_enable
+Date:		September 2022
+Contact:	Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
+Description:	Reading this file tells if the AMD Platform Management(PMF)
+		Cool n Quiet Framework(CnQF) feature is enabled or not.
+
+		This feature is not enabled by default and gets only turned on
+		if OEM BIOS passes a "flag" to PMF ACPI function (index 11 or 12)
+		or in case the user writes "on".
+
+		To turn off CnQF user can write "off" to the sysfs node.
+		Note: Systems that support auto mode will not have this sysfs file
+		available.