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, 21 insertions, 0 deletions

diff --git a/tools/testing/vma/Makefile b/tools/testing/vma/Makefile
new file mode 100644
index 000000000..e72b45ded
--- /dev/null
+++ b/tools/testing/vma/Makefile
@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+.PHONY: default clean
+
+default: vma
+
+include ../shared/shared.mk
+
+OFILES = $(SHARED_OFILES) main.o shared.o maple-shim.o
+TARGETS = vma
+
+# These can be varied to test different sizes.
+CFLAGS += -DNUM_VMA_FLAG_BITS=128 -DNUM_MM_FLAG_BITS=128
+
+main.o: main.c shared.c shared.h vma_internal.h tests/merge.c tests/mmap.c tests/vma.c ../../../mm/vma.c ../../../mm/vma_init.c ../../../mm/vma_exec.c ../../../mm/vma.h include/custom.h include/dup.h include/stubs.h
+
+vma:	$(OFILES)
+	$(CC) $(CFLAGS) -o $@ $(OFILES) $(LDLIBS)
+
+clean:
+	$(RM) $(TARGETS) *.o radix-tree.c idr.c generated/map-shift.h generated/bit-length.h generated/autoconf.h