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, 25 insertions, 0 deletions

diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile
new file mode 100644
index 000000000..4e58d16fc
--- /dev/null
+++ b/drivers/misc/lkdtm/Makefile
@@ -0,0 +1,25 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_LKDTM)		+= lkdtm.o
+
+lkdtm-$(CONFIG_LKDTM)		+= core.o
+lkdtm-$(CONFIG_LKDTM)		+= bugs.o
+lkdtm-$(CONFIG_LKDTM)		+= heap.o
+lkdtm-$(CONFIG_LKDTM)		+= perms.o
+lkdtm-$(CONFIG_LKDTM)		+= refcount.o
+lkdtm-$(CONFIG_LKDTM)		+= rodata_objcopy.o
+lkdtm-$(CONFIG_LKDTM)		+= usercopy.o
+lkdtm-$(CONFIG_LKDTM)		+= kstack_erase.o
+lkdtm-$(CONFIG_LKDTM)		+= cfi.o
+lkdtm-$(CONFIG_LKDTM)		+= fortify.o
+lkdtm-$(CONFIG_PPC_BOOK3S_64)	+= powerpc.o
+
+KASAN_SANITIZE_stackleak.o	:= n
+
+CFLAGS_REMOVE_rodata.o			+= $(CC_FLAGS_LTO) $(RETHUNK_CFLAGS) $(CC_FLAGS_CFI)
+
+OBJCOPYFLAGS :=
+OBJCOPYFLAGS_rodata_objcopy.o	:= \
+			--rename-section .noinstr.text=.rodata,alloc,readonly,load,contents
+targets += rodata.o rodata_objcopy.o
+$(obj)/rodata_objcopy.o: $(obj)/rodata.o FORCE
+	$(call if_changed,objcopy)