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, 59 insertions, 0 deletions

diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
new file mode 100644
index 000000000..fcfbe3f81
--- /dev/null
+++ b/arch/riscv/boot/Makefile
@@ -0,0 +1,59 @@
+#
+# arch/riscv/boot/Makefile
+#
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+#
+# This file is subject to the terms and conditions of the GNU General Public
+# License.  See the file "COPYING" in the main directory of this archive
+# for more details.
+#
+# Copyright (C) 2018, Anup Patel.
+# Author: Anup Patel <anup@brainfault.org>
+#
+# Based on the ia64 and arm64 boot/Makefile.
+#
+
+OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
+OBJCOPYFLAGS_loader.bin :=-O binary
+OBJCOPYFLAGS_xipImage :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
+
+targets := Image Image.* loader loader.o loader.lds loader.bin xipImage
+
+$(obj)/Image: vmlinux FORCE
+	$(call if_changed,objcopy)
+
+$(obj)/Image.gz: $(obj)/Image FORCE
+	$(call if_changed,gzip)
+
+$(obj)/loader.o: $(src)/loader.S $(obj)/Image
+
+$(obj)/loader: $(obj)/loader.o $(obj)/Image $(obj)/loader.lds FORCE
+	$(Q)$(LD) -T $(obj)/loader.lds -o $@ $(obj)/loader.o
+
+$(obj)/Image.bz2: $(obj)/Image FORCE
+	$(call if_changed,bzip2)
+
+$(obj)/Image.lz4: $(obj)/Image FORCE
+	$(call if_changed,lz4)
+
+$(obj)/Image.lzma: $(obj)/Image FORCE
+	$(call if_changed,lzma)
+
+$(obj)/Image.lzo: $(obj)/Image FORCE
+	$(call if_changed,lzo)
+
+$(obj)/Image.zst: $(obj)/Image FORCE
+	$(call if_changed,zstd)
+
+$(obj)/Image.xz: $(obj)/Image FORCE
+	$(call if_changed,xzkern)
+
+$(obj)/loader.bin: $(obj)/loader FORCE
+	$(call if_changed,objcopy)
+
+EFI_ZBOOT_PAYLOAD	:= Image
+EFI_ZBOOT_BFD_TARGET	:= elf$(BITS)-littleriscv
+EFI_ZBOOT_MACH_TYPE	:= RISCV$(BITS)
+
+include $(srctree)/drivers/firmware/efi/libstub/Makefile.zboot