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, 62 insertions, 0 deletions

diff --git a/include/drm/intel/step.h b/include/drm/intel/step.h
new file mode 100644
index 000000000..4de752010
--- /dev/null
+++ b/include/drm/intel/step.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: MIT */
+/* Copyright © 2026 Intel Corporation */
+
+#ifndef __STEP_H__
+#define __STEP_H__
+
+#define STEP_ENUM_VAL(name)  STEP_##name,
+
+#define STEP_NAME_LIST(func)		\
+	func(A0)			\
+	func(A1)			\
+	func(A2)			\
+	func(A3)			\
+	func(B0)			\
+	func(B1)			\
+	func(B2)			\
+	func(B3)			\
+	func(C0)			\
+	func(C1)			\
+	func(C2)			\
+	func(C3)			\
+	func(D0)			\
+	func(D1)			\
+	func(D2)			\
+	func(D3)			\
+	func(E0)			\
+	func(E1)			\
+	func(E2)			\
+	func(E3)			\
+	func(F0)			\
+	func(F1)			\
+	func(F2)			\
+	func(F3)			\
+	func(G0)			\
+	func(G1)			\
+	func(G2)			\
+	func(G3)			\
+	func(H0)			\
+	func(H1)			\
+	func(H2)			\
+	func(H3)			\
+	func(I0)			\
+	func(I1)			\
+	func(I2)			\
+	func(I3)			\
+	func(J0)			\
+	func(J1)			\
+	func(J2)			\
+	func(J3)
+
+/*
+ * Symbolic steppings that do not match the hardware. These are valid both as gt
+ * and display steppings as symbolic names.
+ */
+enum intel_step {
+	STEP_NONE = 0,
+	STEP_NAME_LIST(STEP_ENUM_VAL)
+	STEP_FUTURE,
+	STEP_FOREVER,
+};
+
+#endif /* __STEP_H__ */