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, 83 insertions, 0 deletions

diff --git a/arch/mips/bmips/Kconfig b/arch/mips/bmips/Kconfig
new file mode 100644
index 000000000..63dfc6950
--- /dev/null
+++ b/arch/mips/bmips/Kconfig
@@ -0,0 +1,83 @@
+# SPDX-License-Identifier: GPL-2.0
+if BMIPS_GENERIC
+
+choice
+	prompt "Built-in device tree"
+	help
+	  Legacy bootloaders do not pass a DTB pointer to the kernel, so
+	  if a "wrapper" is not being used, the kernel will need to include
+	  a device tree that matches the target board.
+
+	  The builtin DTB will only be used if the firmware does not supply
+	  a valid DTB.
+
+config DT_NONE
+	bool "None"
+
+config DT_BCM93384WVG
+	bool "BCM93384WVG Zephyr CPU"
+	select BUILTIN_DTB
+
+config DT_BCM93384WVG_VIPER
+	bool "BCM93384WVG Viper CPU (EXPERIMENTAL)"
+	select BUILTIN_DTB
+
+config DT_BCM96368MVWG
+	bool "BCM96368MVWG"
+	select BUILTIN_DTB
+
+config DT_BCM9EJTAGPRB
+	bool "BCM9EJTAGPRB"
+	select BUILTIN_DTB
+
+config DT_BCM97125CBMB
+	bool "BCM97125CBMB"
+	select BUILTIN_DTB
+
+config DT_BCM97346DBSMB
+	bool "BCM97346DBSMB"
+	select BUILTIN_DTB
+
+config DT_BCM97358SVMB
+	bool "BCM97358SVMB"
+	select BUILTIN_DTB
+
+config DT_BCM97360SVMB
+	bool "BCM97360SVMB"
+	select BUILTIN_DTB
+
+config DT_BCM97362SVMB
+	bool "BCM97362SVMB"
+	select BUILTIN_DTB
+
+config DT_BCM97420C
+	bool "BCM97420C"
+	select BUILTIN_DTB
+
+config DT_BCM97425SVMB
+	bool "BCM97425SVMB"
+	select BUILTIN_DTB
+
+config DT_BCM97435SVMB
+	bool "BCM97435SVMB"
+	select BUILTIN_DTB
+
+config DT_COMTREND_VR3032U
+	bool "Comtrend VR-3032u"
+	select BUILTIN_DTB
+
+config DT_NETGEAR_CVG834G
+	bool "NETGEAR CVG834G"
+	select BUILTIN_DTB
+
+config DT_SFR_NEUFBOX4_SERCOMM
+	bool "SFR Neufbox 4 (Sercomm)"
+	select BUILTIN_DTB
+
+config DT_SFR_NEUFBOX6_SERCOMM
+	bool "SFR Neufbox 6 (Sercomm)"
+	select BUILTIN_DTB
+
+endchoice
+
+endif