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, 52 insertions, 0 deletions

diff --git a/fs/lockd/Makefile b/fs/lockd/Makefile
new file mode 100644
index 000000000..3f9569d3b
--- /dev/null
+++ b/fs/lockd/Makefile
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the linux lock manager stuff
+#
+
+ccflags-y += -I$(src)			# needed for trace events
+
+obj-$(CONFIG_LOCKD) += lockd.o
+
+lockd-y := clntlock.o clntproc.o clntxdr.o host.o svc.o svclock.o \
+	   svcshare.o svcproc.o svcsubs.o mon.o trace.o netlink.o \
+	   nlm3xdr_gen.o
+lockd-$(CONFIG_LOCKD_V4) += clnt4xdr.o svc4proc.o nlm4xdr_gen.o
+lockd-$(CONFIG_PROC_FS) += procfs.o
+
+#
+# XDR code generation (requires Python and additional packages)
+#
+# The generated *xdr_gen.{h,c} files are checked into git. Normal kernel
+# builds do not require the xdrgen tool or its Python dependencies.
+#
+# Developers modifying .x files in Documentation/sunrpc/xdr/ should run
+# "make xdrgen" to regenerate the affected files.
+#
+.PHONY: xdrgen
+
+XDRGEN			= ../../tools/net/sunrpc/xdrgen/xdrgen
+
+XDRGEN_DEFINITIONS	= ../../include/linux/sunrpc/xdrgen/nlm4.h \
+			  ../../include/linux/sunrpc/xdrgen/nlm3.h
+XDRGEN_DECLARATIONS	= nlm4xdr_gen.h nlm3xdr_gen.h
+XDRGEN_SOURCE		= nlm4xdr_gen.c nlm3xdr_gen.c
+
+xdrgen: $(XDRGEN_DEFINITIONS) $(XDRGEN_DECLARATIONS) $(XDRGEN_SOURCE)
+
+../../include/linux/sunrpc/xdrgen/nlm4.h: ../../Documentation/sunrpc/xdr/nlm4.x
+	$(XDRGEN) definitions $< > $@
+
+../../include/linux/sunrpc/xdrgen/nlm3.h: ../../Documentation/sunrpc/xdr/nlm3.x
+	$(XDRGEN) definitions $< > $@
+
+nlm4xdr_gen.h: ../../Documentation/sunrpc/xdr/nlm4.x
+	$(XDRGEN) declarations $< > $@
+
+nlm3xdr_gen.h: ../../Documentation/sunrpc/xdr/nlm3.x
+	$(XDRGEN) declarations $< > $@
+
+nlm4xdr_gen.c: ../../Documentation/sunrpc/xdr/nlm4.x
+	$(XDRGEN) source --peer server $< > $@
+
+nlm3xdr_gen.c: ../../Documentation/sunrpc/xdr/nlm3.x
+	$(XDRGEN) source --peer server $< > $@