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, 77 insertions, 0 deletions

diff --git a/arch/xtensa/Makefile b/arch/xtensa/Makefile
new file mode 100644
index 000000000..4c14a0217
--- /dev/null
+++ b/arch/xtensa/Makefile
@@ -0,0 +1,77 @@
+#
+# 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) 2001 - 2005  Tensilica Inc.
+# Copyright (C) 2014 Cadence Design Systems Inc.
+#
+# This file is included by the global makefile so that you can add your own
+# architecture-specific flags and dependencies.
+
+# Core configuration.
+# (Use VAR=<xtensa_config> to use another default compiler.)
+
+variant-y := $(CONFIG_XTENSA_VARIANT_NAME)
+
+VARIANT = $(variant-y)
+
+ifneq ($(VARIANT),)
+  ifdef cross_compiling
+    ifndef CROSS_COMPILE
+      CROSS_COMPILE = xtensa_$(VARIANT)-
+    endif
+  endif
+endif
+
+# Platform configuration
+
+platform-$(CONFIG_XTENSA_PLATFORM_XT2000)	:= xt2000
+platform-$(CONFIG_XTENSA_PLATFORM_ISS)		:= iss
+platform-$(CONFIG_XTENSA_PLATFORM_XTFPGA)	:= xtfpga
+
+# temporarily until string.h is fixed
+KBUILD_CFLAGS += -ffreestanding -D__linux__
+KBUILD_CFLAGS += -pipe -mlongcalls -mtext-section-literals
+KBUILD_CFLAGS += $(call cc-option,-mforce-no-pic,)
+KBUILD_CFLAGS += $(call cc-option,-mno-serialize-volatile,)
+KBUILD_CFLAGS += $(call cc-option,-mno-fdpic,)
+ifneq ($(CONFIG_KERNEL_ABI_CALL0),)
+KBUILD_CFLAGS += -mabi=call0
+KBUILD_AFLAGS += -mabi=call0
+endif
+
+KBUILD_AFLAGS += -mlongcalls -mtext-section-literals
+KBUILD_AFLAGS += $(call cc-option,-mno-fdpic,)
+
+KBUILD_LDFLAGS += -m elf32xtensa
+
+ifneq ($(CONFIG_LD_NO_RELAX),)
+KBUILD_LDFLAGS += --no-relax
+endif
+
+CHECKFLAGS += -D$(if $(CONFIG_CPU_BIG_ENDIAN),__XTENSA_EB__,__XTENSA_EL__)
+
+vardirs := $(patsubst %,arch/xtensa/variants/%/,$(variant-y))
+plfdirs := $(patsubst %,arch/xtensa/platforms/%/,$(platform-y))
+
+KBUILD_CPPFLAGS += $(patsubst %,-I$(srctree)/%include,$(vardirs) $(plfdirs))
+
+KBUILD_DEFCONFIG := iss_defconfig
+
+libs-y		+= arch/xtensa/lib/
+
+boot		:= arch/xtensa/boot
+
+all Image zImage uImage xipImage: vmlinux
+	$(Q)$(MAKE) $(build)=$(boot) $@
+
+archheaders:
+	$(Q)$(MAKE) $(build)=arch/xtensa/kernel/syscalls all
+
+define archhelp
+  @echo '* Image       - Kernel ELF image with reset vector'
+  @echo '* zImage      - Compressed kernel image (arch/xtensa/boot/images/zImage.*)'
+  @echo '* uImage      - U-Boot wrapped image'
+  @echo '  xipImage    - XIP image'
+endef