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, 63 insertions, 0 deletions

diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
new file mode 100644
index 000000000..6ead00ec7
--- /dev/null
+++ b/scripts/Makefile.clean
@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: GPL-2.0
+# ==========================================================================
+# Cleaning up
+# ==========================================================================
+
+src := $(srcroot)/$(obj)
+
+PHONY := __clean
+__clean:
+
+include $(srctree)/scripts/Kbuild.include
+include $(kbuild-file)
+
+# Figure out what we need to build from the various variables
+# ==========================================================================
+
+subdir-ymn := $(sort $(subdir-y) $(subdir-m) $(subdir-) \
+		$(patsubst %/,%, $(filter %/, $(obj-y) $(obj-m) $(obj-))))
+
+# Add subdir path
+
+subdir-ymn	:= $(addprefix $(obj)/,$(subdir-ymn))
+
+# build a list of files to remove, usually relative to the current
+# directory
+
+__clean-files	:= \
+	$(clean-files) $(targets) $(hostprogs) $(userprogs) \
+	$(extra-y) $(extra-m) $(extra-) \
+	$(always-y) $(always-m) $(always-) \
+	$(hostprogs-always-y) $(hostprogs-always-m) $(hostprogs-always-) \
+	$(userprogs-always-y) $(userprogs-always-m) $(userprogs-always-)
+
+__clean-files   := $(filter-out $(no-clean-files), $(__clean-files))
+
+__clean-files   := $(wildcard $(addprefix $(obj)/, $(__clean-files)))
+
+# ==========================================================================
+
+# To make this rule robust against "Argument list too long" error,
+# remove $(obj)/ prefix, and restore it by a shell command.
+quiet_cmd_clean = CLEAN   $(obj)
+      cmd_clean = printf '$(obj)/%s ' $(patsubst $(obj)/%,%,$(__clean-files)) | xargs rm -rf
+
+__clean: $(subdir-ymn)
+ifneq ($(strip $(__clean-files)),)
+	$(call cmd,clean)
+endif
+	@:
+
+
+# ===========================================================================
+# Generic stuff
+# ===========================================================================
+
+# Descending
+# ---------------------------------------------------------------------------
+
+PHONY += $(subdir-ymn)
+$(subdir-ymn):
+	$(Q)$(MAKE) $(clean)=$@
+
+.PHONY: $(PHONY)