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, 43 insertions, 0 deletions

diff --git a/scripts/Makefile.dtbinst b/scripts/Makefile.dtbinst
new file mode 100644
index 000000000..9d920419a
--- /dev/null
+++ b/scripts/Makefile.dtbinst
@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: GPL-2.0
+# ==========================================================================
+# Installing dtb files
+#
+# Installs all dtb files listed in $(dtb-y) either in the
+# INSTALL_DTBS_PATH directory or the default location:
+#
+#   $INSTALL_PATH/dtbs/$KERNELRELEASE
+# ==========================================================================
+
+PHONY := __dtbs_install
+__dtbs_install:
+
+include include/config/auto.conf
+include $(srctree)/scripts/Kbuild.include
+
+dst := $(INSTALL_DTBS_PATH)
+
+quiet_cmd_dtb_install = INSTALL $@
+      cmd_dtb_install = install -D -m 0644 $< $@
+
+$(dst)/%: $(obj)/%
+	$(call cmd,dtb_install)
+
+dtbs := $(patsubst $(obj)/%,%,$(call read-file, $(obj)/dtbs-list))
+
+ifdef CONFIG_ARCH_WANT_FLAT_DTB_INSTALL
+
+define gen_install_rules
+$(dst)/%: $(obj)/$(1)%
+	$$(call cmd,dtb_install)
+endef
+
+$(foreach d, $(sort $(dir $(dtbs))), $(eval $(call gen_install_rules,$(d))))
+
+dtbs := $(notdir $(dtbs))
+
+endif # CONFIG_ARCH_WANT_FLAT_DTB_INSTALL
+
+__dtbs_install: $(addprefix $(dst)/, $(dtbs))
+	@:
+
+.PHONY: $(PHONY)