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, 120 insertions, 0 deletions

diff --git a/arch/alpha/boot/Makefile b/arch/alpha/boot/Makefile
new file mode 100644
index 000000000..d8dba85e6
--- /dev/null
+++ b/arch/alpha/boot/Makefile
@@ -0,0 +1,120 @@
+#
+# arch/alpha/boot/Makefile
+#
+# 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) 1994 by Linus Torvalds
+#
+
+hostprogs	:= tools/mkbb tools/objstrip
+targets		:= vmlinux.gz vmlinux \
+		   vmlinux.nh tools/lxboot tools/bootlx tools/bootph \
+		   tools/bootpzh bootloader bootpheader bootpzheader 
+OBJSTRIP	:= $(obj)/tools/objstrip
+
+KBUILD_HOSTCFLAGS := -Wall -I$(objtree)/usr/include
+BOOTCFLAGS	+= -I$(objtree)/$(obj) -I$(srctree)/$(obj)
+
+# SRM bootable image.  Copy to offset 512 of a partition.
+$(obj)/bootimage: $(addprefix $(obj)/tools/,mkbb lxboot bootlx) $(obj)/vmlinux.nh
+	( cat $(obj)/tools/lxboot $(obj)/tools/bootlx $(obj)/vmlinux.nh ) > $@ 
+	$(obj)/tools/mkbb $@ $(obj)/tools/lxboot
+	@echo '  Bootimage $@ is ready'
+
+# BOOTP bootable image.  Define INITRD during make to append initrd image.
+$(obj)/bootpfile: $(obj)/tools/bootph $(obj)/vmlinux.nh
+	cat $(obj)/tools/bootph $(obj)/vmlinux.nh > $@
+ifdef INITRD
+	cat $(INITRD) >> $@
+endif
+
+# Compressed kernel BOOTP bootable image.
+# Define INITRD during make to append initrd image.
+$(obj)/bootpzfile: $(obj)/tools/bootpzh $(obj)/vmlinux.nh.gz
+	cat $(obj)/tools/bootpzh $(obj)/vmlinux.nh.gz > $@
+ifdef INITRD
+	cat $(INITRD) >> $@
+endif
+
+# Compressed kernel image
+$(obj)/vmlinux.gz: $(obj)/vmlinux FORCE
+	$(call if_changed,gzip)
+	@echo '  Kernel $@ is ready'
+
+$(obj)/main.o: $(obj)/ksize.h
+$(obj)/bootp.o: $(obj)/ksize.h
+$(obj)/bootpz.o: $(obj)/kzsize.h
+
+$(obj)/ksize.h: $(obj)/vmlinux.nh FORCE
+	echo "#define KERNEL_SIZE `ls -l $(obj)/vmlinux.nh | awk '{print $$5}'`" > $@T
+ifdef INITRD
+	[ -f $(INITRD) ] || exit 1
+	echo "#define INITRD_IMAGE_SIZE `ls -l $(INITRD) | awk '{print $$5}'`" >> $@T
+endif
+	cmp -s $@T $@ || mv -f $@T $@
+	rm -f $@T
+
+$(obj)/kzsize.h: $(obj)/vmlinux.nh.gz FORCE
+	echo "#define KERNEL_SIZE `ls -l $(obj)/vmlinux.nh | awk '{print $$5}'`" > $@T
+	echo "#define KERNEL_Z_SIZE `ls -l $(obj)/vmlinux.nh.gz | awk '{print $$5}'`" >> $@T
+ifdef INITRD
+	[ -f $(INITRD) ] || exit 1
+	echo "#define INITRD_IMAGE_SIZE `ls -l $(INITRD) | awk '{print $$5}'`" >> $@T
+endif
+	cmp -s $@T $@ || mv -f $@T $@
+	rm -f $@T
+
+quiet_cmd_strip = STRIP  $@
+      cmd_strip = $(STRIP) -o $@ $<
+
+$(obj)/vmlinux: vmlinux FORCE
+	$(call if_changed,strip)
+
+quiet_cmd_objstrip = OBJSTRIP $@
+      cmd_objstrip = $(OBJSTRIP) $(OSFLAGS_$(@F)) $< $@
+
+OSFLAGS_vmlinux.nh	:= -v
+OSFLAGS_lxboot		:= -p
+OSFLAGS_bootlx		:= -vb
+OSFLAGS_bootph		:= -vb
+OSFLAGS_bootpzh		:= -vb
+
+$(obj)/vmlinux.nh: vmlinux $(OBJSTRIP) FORCE
+	$(call if_changed,objstrip)
+
+$(obj)/vmlinux.nh.gz: $(obj)/vmlinux.nh FORCE
+	$(call if_changed,gzip)
+
+$(obj)/tools/lxboot: $(obj)/bootloader $(OBJSTRIP) FORCE
+	$(call if_changed,objstrip)
+
+$(obj)/tools/bootlx: $(obj)/bootloader $(OBJSTRIP) FORCE
+	$(call if_changed,objstrip)
+
+$(obj)/tools/bootph: $(obj)/bootpheader $(OBJSTRIP) FORCE
+	$(call if_changed,objstrip)
+
+$(obj)/tools/bootpzh: $(obj)/bootpzheader $(OBJSTRIP) FORCE
+	$(call if_changed,objstrip)
+
+LDFLAGS_bootloader   := -static -T # -N -relax
+LDFLAGS_bootloader   := -static -T # -N -relax
+LDFLAGS_bootpheader  := -static -T # -N -relax
+LDFLAGS_bootpzheader := -static -T # -N -relax
+
+OBJ_bootlx   := $(obj)/head.o $(obj)/stdio.o $(obj)/main.o
+OBJ_bootph   := $(obj)/head.o $(obj)/stdio.o $(obj)/bootp.o
+OBJ_bootpzh  := $(obj)/head.o $(obj)/stdio.o $(obj)/bootpz.o $(obj)/misc.o
+
+$(obj)/bootloader: $(obj)/bootloader.lds $(OBJ_bootlx) $(LIBS_Y) FORCE
+	$(call if_changed,ld)
+
+$(obj)/bootpheader: $(obj)/bootloader.lds $(OBJ_bootph) $(LIBS_Y) FORCE
+	$(call if_changed,ld)
+
+$(obj)/bootpzheader: $(obj)/bootloader.lds $(OBJ_bootpzh) $(LIBS_Y) FORCE
+	$(call if_changed,ld)
+
+$(obj)/misc.o: lib/inflate.c