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, 24 insertions, 0 deletions

diff --git a/drivers/firmware/xilinx/zynqmp-debug.h b/drivers/firmware/xilinx/zynqmp-debug.h
new file mode 100644
index 000000000..e1515a93e
--- /dev/null
+++ b/drivers/firmware/xilinx/zynqmp-debug.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Xilinx Zynq MPSoC Firmware layer
+ *
+ *  Copyright (C) 2014-2018 Xilinx
+ *
+ *  Michal Simek <michal.simek@amd.com>
+ *  Davorin Mista <davorin.mista@aggios.com>
+ *  Jolly Shah <jollys@xilinx.com>
+ *  Rajan Vaja <rajanv@xilinx.com>
+ */
+
+#ifndef __FIRMWARE_ZYNQMP_DEBUG_H__
+#define __FIRMWARE_ZYNQMP_DEBUG_H__
+
+#if IS_REACHABLE(CONFIG_ZYNQMP_FIRMWARE_DEBUG)
+void zynqmp_pm_api_debugfs_init(void);
+void zynqmp_pm_api_debugfs_exit(void);
+#else
+static inline void zynqmp_pm_api_debugfs_init(void) { }
+static inline void zynqmp_pm_api_debugfs_exit(void) { }
+#endif
+
+#endif /* __FIRMWARE_ZYNQMP_DEBUG_H__ */