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, 51 insertions, 0 deletions

diff --git a/arch/arm/nwfpe/fpopcode.c b/arch/arm/nwfpe/fpopcode.c
new file mode 100644
index 000000000..c680bf1bb
--- /dev/null
+++ b/arch/arm/nwfpe/fpopcode.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+    NetWinder Floating Point Emulator
+    (c) Rebel.COM, 1998,1999
+
+    Direct questions, comments to Scott Bambrough <scottb@netwinder.org>
+
+*/
+
+#include "fpa11.h"
+#include "softfloat.h"
+#include "fpopcode.h"
+#include "fpsr.h"
+#include "fpmodule.h"
+#include "fpmodule.inl"
+
+#ifdef CONFIG_FPE_NWFPE_XP
+const floatx80 floatx80Constant[] = {
+	{ .high = 0x0000, .low = 0x0000000000000000ULL},/* extended 0.0 */
+	{ .high = 0x3fff, .low = 0x8000000000000000ULL},/* extended 1.0 */
+	{ .high = 0x4000, .low = 0x8000000000000000ULL},/* extended 2.0 */
+	{ .high = 0x4000, .low = 0xc000000000000000ULL},/* extended 3.0 */
+	{ .high = 0x4001, .low = 0x8000000000000000ULL},/* extended 4.0 */
+	{ .high = 0x4001, .low = 0xa000000000000000ULL},/* extended 5.0 */
+	{ .high = 0x3ffe, .low = 0x8000000000000000ULL},/* extended 0.5 */
+	{ .high = 0x4002, .low = 0xa000000000000000ULL},/* extended 10.0 */
+};
+#endif
+
+const float64 float64Constant[] = {
+	0x0000000000000000ULL,	/* double 0.0 */
+	0x3ff0000000000000ULL,	/* double 1.0 */
+	0x4000000000000000ULL,	/* double 2.0 */
+	0x4008000000000000ULL,	/* double 3.0 */
+	0x4010000000000000ULL,	/* double 4.0 */
+	0x4014000000000000ULL,	/* double 5.0 */
+	0x3fe0000000000000ULL,	/* double 0.5 */
+	0x4024000000000000ULL	/* double 10.0 */
+};
+
+const float32 float32Constant[] = {
+	0x00000000,		/* single 0.0 */
+	0x3f800000,		/* single 1.0 */
+	0x40000000,		/* single 2.0 */
+	0x40400000,		/* single 3.0 */
+	0x40800000,		/* single 4.0 */
+	0x40a00000,		/* single 5.0 */
+	0x3f000000,		/* single 0.5 */
+	0x41200000		/* single 10.0 */
+};
+