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, 57 insertions, 0 deletions

diff --git a/arch/arm/tools/Makefile b/arch/arm/tools/Makefile
new file mode 100644
index 000000000..28b6da8ac
--- /dev/null
+++ b/arch/arm/tools/Makefile
@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# linux/arch/arm/tools/Makefile
+#
+# Copyright (C) 2001 Russell King
+#
+
+gen := arch/$(ARCH)/include/generated
+kapi := $(gen)/asm
+uapi := $(gen)/uapi/asm
+syshdr := $(srctree)/scripts/syscallhdr.sh
+sysnr := $(src)/syscallnr.sh
+systbl := $(srctree)/scripts/syscalltbl.sh
+syscall := $(src)/syscall.tbl
+
+gen-y := $(gen)/calls-oabi.S
+gen-y += $(gen)/calls-eabi.S
+kapi-hdrs-y := $(kapi)/unistd-nr.h
+kapi-hdrs-y += $(kapi)/mach-types.h
+uapi-hdrs-y += $(uapi)/unistd-oabi.h
+uapi-hdrs-y += $(uapi)/unistd-eabi.h
+
+targets += $(addprefix ../../../,$(gen-y) $(kapi-hdrs-y) $(uapi-hdrs-y))
+
+PHONY += kapi uapi
+
+kapi:	$(kapi-hdrs-y) $(gen-y)
+
+uapi:	$(uapi-hdrs-y)
+
+# Create output directory if not already present
+$(shell mkdir -p $(kapi) $(uapi))
+
+quiet_cmd_gen_mach = GEN     $@
+      cmd_gen_mach = $(AWK) -f $(real-prereqs) > $@
+
+$(kapi)/mach-types.h: $(src)/gen-mach-types $(src)/mach-types FORCE
+	$(call if_changed,gen_mach)
+
+quiet_cmd_syshdr = SYSHDR  $@
+      cmd_syshdr = $(CONFIG_SHELL) $(syshdr) --abis common,$* \
+		   --offset __NR_SYSCALL_BASE $< $@
+
+quiet_cmd_systbl = SYSTBL  $@
+      cmd_systbl = $(CONFIG_SHELL) $(systbl) --abis common,$* $< $@
+
+quiet_cmd_sysnr  = SYSNR   $@
+      cmd_sysnr  = $(CONFIG_SHELL) $(sysnr) $< $@
+
+$(uapi)/unistd-%.h: $(syscall) $(syshdr) FORCE
+	$(call if_changed,syshdr)
+
+$(kapi)/unistd-nr.h: $(syscall) $(sysnr) FORCE
+	$(call if_changed,sysnr)
+
+$(gen)/calls-%.S: $(syscall) $(systbl) FORCE
+	$(call if_changed,systbl)