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, 35 insertions, 0 deletions

diff --git a/arch/microblaze/boot/Makefile b/arch/microblaze/boot/Makefile
new file mode 100644
index 000000000..2b42c370d
--- /dev/null
+++ b/arch/microblaze/boot/Makefile
@@ -0,0 +1,35 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# arch/microblaze/boot/Makefile
+#
+
+targets := linux.bin linux.bin.gz linux.bin.ub simpleImage.*
+
+OBJCOPYFLAGS := -R .note -R .comment -R .note.gnu.build-id -O binary
+
+$(obj)/linux.bin: vmlinux FORCE
+	$(call if_changed,objcopy)
+
+$(obj)/linux.bin.ub: $(obj)/linux.bin FORCE
+	$(call if_changed,uimage)
+
+$(obj)/linux.bin.gz: $(obj)/linux.bin FORCE
+	$(call if_changed,gzip)
+
+quiet_cmd_strip = STRIP   $< $@$2
+	cmd_strip = $(STRIP) -K microblaze_start -K _end -K __log_buf \
+				-K _fdt_start $< -o $@$2
+
+UIMAGE_LOADADDR = $(CONFIG_KERNEL_BASE_ADDR)
+
+$(obj)/simpleImage.$(DTB): vmlinux FORCE
+	$(call if_changed,objcopy)
+
+$(obj)/simpleImage.$(DTB).ub: $(obj)/simpleImage.$(DTB) FORCE
+	$(call if_changed,uimage)
+
+$(obj)/simpleImage.$(DTB).unstrip: vmlinux FORCE
+	$(call if_changed,copy)
+
+$(obj)/simpleImage.$(DTB).strip: vmlinux FORCE
+	$(call if_changed,strip)