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, 51 insertions, 0 deletions

diff --git a/arch/x86/tools/Makefile b/arch/x86/tools/Makefile
new file mode 100644
index 000000000..39a183fff
--- /dev/null
+++ b/arch/x86/tools/Makefile
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: GPL-2.0
+PHONY += posttest
+
+ifneq ($(findstring 1, $(KBUILD_VERBOSE)),)
+  posttest_verbose = -v
+else
+  posttest_verbose =
+endif
+
+ifeq ($(CONFIG_64BIT),y)
+  posttest_64bit = -y
+else
+  posttest_64bit = -n
+endif
+
+reformatter = $(srctree)/arch/x86/tools/objdump_reformat.awk
+chkobjdump = $(srctree)/arch/x86/tools/chkobjdump.awk
+
+quiet_cmd_posttest = TEST    $@
+      cmd_posttest = $(OBJDUMP) -d -j .text $(objtree)/vmlinux | $(AWK) -f $(reformatter) | $(obj)/insn_decoder_test $(posttest_64bit) $(posttest_verbose)
+
+quiet_cmd_sanitytest = TEST    $@
+      cmd_sanitytest = $(obj)/insn_sanity $(posttest_64bit) -m 1000000
+
+posttest: $(obj)/insn_decoder_test vmlinux $(obj)/insn_sanity
+	$(call cmd,posttest)
+	$(call cmd,sanitytest)
+
+hostprogs += insn_decoder_test insn_sanity
+
+# -I needed for generated C source and C source which in the kernel tree.
+HOSTCFLAGS_insn_decoder_test.o := -Wall -I$(srctree)/tools/arch/x86/lib/ -I$(srctree)/tools/arch/x86/include/ -I$(objtree)/arch/x86/lib/
+
+HOSTCFLAGS_insn_sanity.o := -Wall -I$(srctree)/tools/arch/x86/lib/ -I$(srctree)/tools/arch/x86/include/ -I$(objtree)/arch/x86/lib/
+
+# Dependencies are also needed.
+$(obj)/insn_decoder_test.o: $(srctree)/tools/arch/x86/lib/insn.c $(srctree)/tools/arch/x86/lib/inat.c $(srctree)/tools/arch/x86/include/asm/inat_types.h $(srctree)/tools/arch/x86/include/asm/inat.h $(srctree)/tools/arch/x86/include/asm/insn.h $(objtree)/arch/x86/lib/inat-tables.c
+
+$(obj)/insn_sanity.o: $(srctree)/tools/arch/x86/lib/insn.c $(srctree)/tools/arch/x86/lib/inat.c $(srctree)/tools/arch/x86/include/asm/inat_types.h $(srctree)/tools/arch/x86/include/asm/inat.h $(srctree)/tools/arch/x86/include/asm/insn.h $(objtree)/arch/x86/lib/inat-tables.c
+
+HOST_EXTRACFLAGS += -I$(srctree)/tools/include -I$(srctree)/include/uapi \
+		    -I$(srctree)/arch/$(SUBARCH)/include/uapi
+
+hostprogs	+= relocs vdso2c
+relocs-objs	:= relocs_32.o relocs_64.o relocs_common.o
+
+always-y	:= $(hostprogs)
+
+PHONY += $(hostprogs)
+$(hostprogs): %: $(obj)/%
+	@: