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, 19 insertions, 0 deletions

diff --git a/tools/testing/memblock/scripts/Makefile.include b/tools/testing/memblock/scripts/Makefile.include
new file mode 100644
index 000000000..998281723
--- /dev/null
+++ b/tools/testing/memblock/scripts/Makefile.include
@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: GPL-2.0
+# Definitions for user-provided arguments
+
+# Simulate CONFIG_NUMA=y
+ifeq ($(NUMA), 1)
+	CFLAGS += -D CONFIG_NUMA -D CONFIG_NODES_SHIFT=4
+endif
+
+# Use 32 bit physical addresses.
+# Remember to install 32-bit version of dependencies.
+ifeq ($(32BIT_PHYS_ADDR_T), 1)
+	CFLAGS += -m32 -U CONFIG_PHYS_ADDR_T_64BIT
+	LDFLAGS += -m32
+endif
+
+# Enable memblock_dbg() messages
+ifeq ($(MEMBLOCK_DEBUG), 1)
+	CFLAGS += -D MEMBLOCK_DEBUG
+endif