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, 93 insertions, 0 deletions

diff --git a/arch/microblaze/Makefile b/arch/microblaze/Makefile
new file mode 100644
index 000000000..02e6be9c5
--- /dev/null
+++ b/arch/microblaze/Makefile
@@ -0,0 +1,93 @@
+# SPDX-License-Identifier: GPL-2.0
+KBUILD_DEFCONFIG := mmu_defconfig
+
+UTS_SYSNAME = -DUTS_SYSNAME=\"Linux\"
+
+# What CPU version are we building for, and crack it open
+# as major.minor.rev
+CPU_VER   := $(CONFIG_XILINX_MICROBLAZE0_HW_VER)
+CPU_MAJOR := $(word 1, $(subst ., , $(CPU_VER)))
+CPU_MINOR := $(word 2, $(subst ., , $(CPU_VER)))
+CPU_REV   := $(word 3, $(subst ., , $(CPU_VER)))
+
+export CPU_VER CPU_MAJOR CPU_MINOR CPU_REV
+
+# Use cpu-related CONFIG_ vars to set compile options.
+# The various CONFIG_XILINX cpu features options are integers 0/1/2...
+# rather than bools y/n
+
+# Work out HW multipler support. This is tricky.
+# 1. Spartan2 has no HW multipliers.
+# 2. MicroBlaze v3.x always uses them, except in Spartan 2
+# 3. All other FPGa/CPU ver combos, we can trust the CONFIG_ settings
+ifeq (,$(findstring spartan2,$(CONFIG_XILINX_MICROBLAZE0_FAMILY)))
+  ifeq ($(CPU_MAJOR),3)
+    CPUFLAGS-1 += -mno-xl-soft-mul
+  else
+    # USE_HW_MUL can be 0, 1, or 2, defining a hierarchy of HW Mul support.
+    CPUFLAGS-$(subst 1,,$(CONFIG_XILINX_MICROBLAZE0_USE_HW_MUL)) += -mxl-multiply-high
+    CPUFLAGS-$(CONFIG_XILINX_MICROBLAZE0_USE_HW_MUL) += -mno-xl-soft-mul
+  endif
+endif
+CPUFLAGS-$(CONFIG_XILINX_MICROBLAZE0_USE_DIV) += -mno-xl-soft-div
+CPUFLAGS-$(CONFIG_XILINX_MICROBLAZE0_USE_BARREL) += -mxl-barrel-shift
+CPUFLAGS-$(CONFIG_XILINX_MICROBLAZE0_USE_PCMP_INSTR) += -mxl-pattern-compare
+
+ifdef CONFIG_CPU_BIG_ENDIAN
+KBUILD_CFLAGS += -mbig-endian
+KBUILD_AFLAGS += -mbig-endian
+KBUILD_LDFLAGS += -EB
+else
+KBUILD_CFLAGS += -mlittle-endian
+KBUILD_AFLAGS += -mlittle-endian
+KBUILD_LDFLAGS += -EL
+endif
+
+CPUFLAGS-1 += $(call cc-option,-mcpu=v$(CPU_VER))
+
+# r31 holds current when in kernel mode
+KBUILD_CFLAGS += -ffixed-r31 $(CPUFLAGS-y) $(CPUFLAGS-1) $(CPUFLAGS-2)
+
+libs-y += arch/microblaze/lib/
+
+boot := arch/microblaze/boot
+
+# Are we making a simpleImage.<boardname> target? If so, crack out the boardname
+DTB:=$(subst simpleImage.,,$(filter simpleImage.%, $(MAKECMDGOALS)))
+
+export DTB
+
+all: linux.bin
+
+archheaders:
+	$(Q)$(MAKE) $(build)=arch/microblaze/kernel/syscalls all
+
+PHONY += linux.bin linux.bin.gz linux.bin.ub
+linux.bin.ub linux.bin.gz: linux.bin
+linux.bin: vmlinux
+linux.bin linux.bin.gz linux.bin.ub:
+	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
+	@echo 'Kernel: $(boot)/$@ is ready' ' (#'$(or $(KBUILD_BUILD_VERSION),`cat .version`)')'
+
+PHONY += simpleImage.$(DTB)
+simpleImage.$(DTB): vmlinux
+	$(Q)$(MAKE) $(build)=$(boot) $(addprefix $(boot)/$@., ub unstrip strip)
+	@echo 'Kernel: $(boot)/$@ is ready' ' (#'$(or $(KBUILD_BUILD_VERSION),`cat .version`)')'
+
+define archhelp
+  echo '* linux.bin    - Create raw binary'
+  echo '  linux.bin.gz - Create compressed raw binary'
+  echo '  linux.bin.ub - Create U-Boot wrapped raw binary'
+  echo '  simpleImage.<dt> - Create the following images with <dt>.dtb linked in'
+  echo '                    simpleImage.<dt>        : raw image'
+  echo '                    simpleImage.<dt>.ub     : raw image with U-Boot header'
+  echo '                    simpleImage.<dt>.unstrip: ELF (identical to vmlinux)'
+  echo '                    simpleImage.<dt>.strip  : stripped ELF'
+  echo '  Targets with <dt> embed a device tree blob inside the image'
+  echo '  These targets support board with firmware that does not'
+  echo '  support passing a device tree directly. Replace <dt> with the'
+  echo '  name of a dts file from the arch/microblaze/boot/dts/ directory'
+  echo '  (minus the .dts extension).'
+endef
+
+MRPROPER_FILES += $(boot)/simpleImage.*