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, 26 insertions, 0 deletions

diff --git a/drivers/firmware/xilinx/Kconfig b/drivers/firmware/xilinx/Kconfig
new file mode 100644
index 000000000..9a9bd1908
--- /dev/null
+++ b/drivers/firmware/xilinx/Kconfig
@@ -0,0 +1,26 @@
+# SPDX-License-Identifier: GPL-2.0
+# Kconfig for Xilinx firmwares
+
+menu "Zynq MPSoC Firmware Drivers"
+	depends on ARCH_ZYNQMP
+
+config ZYNQMP_FIRMWARE
+	bool "Enable Xilinx Zynq MPSoC firmware interface"
+	depends on ARCH_ZYNQMP
+	default y if ARCH_ZYNQMP
+	select MFD_CORE
+	help
+	  Firmware interface driver is used by different
+	  drivers to communicate with the firmware for
+	  various platform management services.
+	  Say yes to enable ZynqMP firmware interface driver.
+	  If in doubt, say N.
+
+config ZYNQMP_FIRMWARE_DEBUG
+	bool "Enable Xilinx Zynq MPSoC firmware debug APIs"
+	depends on ZYNQMP_FIRMWARE && DEBUG_FS
+	help
+	  Say yes to enable ZynqMP firmware interface debug APIs.
+	  If in doubt, say N.
+
+endmenu