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/net/sunrpc/Makefile b/net/sunrpc/Makefile
new file mode 100644
index 000000000..96727df3a
--- /dev/null
+++ b/net/sunrpc/Makefile
@@ -0,0 +1,21 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for Linux kernel SUN RPC
+#
+
+
+obj-$(CONFIG_SUNRPC) += sunrpc.o
+obj-$(CONFIG_SUNRPC_GSS) += auth_gss/
+obj-$(CONFIG_SUNRPC_XPRT_RDMA) += xprtrdma/
+
+sunrpc-y := clnt.o xprt.o socklib.o xprtsock.o sched.o \
+	    auth.o auth_null.o auth_tls.o auth_unix.o \
+	    svc.o svcsock.o svcauth.o svcauth_unix.o \
+	    addr.o rpcb_clnt.o timer.o xdr.o \
+	    sunrpc_syms.o cache.o rpc_pipe.o sysfs.o \
+	    svc_xprt.o \
+	    xprtmultipath.o netlink.o
+sunrpc-$(CONFIG_SUNRPC_DEBUG) += debugfs.o
+sunrpc-$(CONFIG_SUNRPC_BACKCHANNEL) += backchannel_rqst.o
+sunrpc-$(CONFIG_PROC_FS) += stats.o
+sunrpc-$(CONFIG_SYSCTL) += sysctl.o