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, 17 insertions, 0 deletions

diff --git a/net/ipv4/igmp_internal.h b/net/ipv4/igmp_internal.h
new file mode 100644
index 000000000..0a1bcc8ec
--- /dev/null
+++ b/net/ipv4/igmp_internal.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _LINUX_IGMP_INTERNAL_H
+#define _LINUX_IGMP_INTERNAL_H
+
+struct inet_fill_args {
+	u32 portid;
+	u32 seq;
+	int event;
+	unsigned int flags;
+	int netnsid;
+	int ifindex;
+};
+
+int inet_fill_ifmcaddr(struct sk_buff *skb, struct net_device *dev,
+		       const struct ip_mc_list *im,
+		       struct inet_fill_args *args);
+#endif