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, 44 insertions, 0 deletions

diff --git a/net/rxrpc/utils.c b/net/rxrpc/utils.c
new file mode 100644
index 000000000..2e4b9d86e
--- /dev/null
+++ b/net/rxrpc/utils.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Utility routines
+ *
+ * Copyright (C) 2015 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/udp.h>
+#include "ar-internal.h"
+
+/*
+ * Fill out a peer address from a socket buffer containing a packet.
+ */
+int rxrpc_extract_addr_from_skb(struct sockaddr_rxrpc *srx, struct sk_buff *skb)
+{
+	memset(srx, 0, sizeof(*srx));
+
+	switch (ntohs(skb->protocol)) {
+	case ETH_P_IP:
+		srx->transport_type = SOCK_DGRAM;
+		srx->transport_len = sizeof(srx->transport.sin);
+		srx->transport.sin.sin_family = AF_INET;
+		srx->transport.sin.sin_port = udp_hdr(skb)->source;
+		srx->transport.sin.sin_addr.s_addr = ip_hdr(skb)->saddr;
+		return 0;
+
+#ifdef CONFIG_AF_RXRPC_IPV6
+	case ETH_P_IPV6:
+		srx->transport_type = SOCK_DGRAM;
+		srx->transport_len = sizeof(srx->transport.sin6);
+		srx->transport.sin6.sin6_family = AF_INET6;
+		srx->transport.sin6.sin6_port = udp_hdr(skb)->source;
+		srx->transport.sin6.sin6_addr = ipv6_hdr(skb)->saddr;
+		return 0;
+#endif
+
+	default:
+		pr_warn_ratelimited("AF_RXRPC: Unknown eth protocol %u\n",
+				    ntohs(skb->protocol));
+		return -EAFNOSUPPORT;
+	}
+}