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, 106 insertions, 0 deletions

diff --git a/net/802/fc.c b/net/802/fc.c
new file mode 100644
index 000000000..afd3d288a
--- /dev/null
+++ b/net/802/fc.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * NET3:	Fibre Channel device handling subroutines
+ *
+ *		Vineet Abraham <vma@iol.unh.edu>
+ *		v 1.0 03/22/99
+ */
+
+#include <linux/uaccess.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/socket.h>
+#include <linux/in.h>
+#include <linux/inet.h>
+#include <linux/netdevice.h>
+#include <linux/fcdevice.h>
+#include <linux/skbuff.h>
+#include <linux/errno.h>
+#include <linux/timer.h>
+#include <linux/net.h>
+#include <linux/proc_fs.h>
+#include <linux/init.h>
+#include <linux/export.h>
+#include <net/arp.h>
+
+/*
+ *	Put the headers on a Fibre Channel packet.
+ */
+
+static int fc_header(struct sk_buff *skb, struct net_device *dev,
+		     unsigned short type,
+		     const void *daddr, const void *saddr, unsigned int len)
+{
+	struct fch_hdr *fch;
+	int hdr_len;
+
+	/*
+	 * Add the 802.2 SNAP header if IP as the IPv4 code calls
+	 * dev->hard_header directly.
+	 */
+	if (type == ETH_P_IP || type == ETH_P_ARP)
+	{
+		struct fcllc *fcllc;
+
+		hdr_len = sizeof(struct fch_hdr) + sizeof(struct fcllc);
+		fch = skb_push(skb, hdr_len);
+		fcllc = (struct fcllc *)(fch+1);
+		fcllc->dsap = fcllc->ssap = EXTENDED_SAP;
+		fcllc->llc = UI_CMD;
+		fcllc->protid[0] = fcllc->protid[1] = fcllc->protid[2] = 0x00;
+		fcllc->ethertype = htons(type);
+	}
+	else
+	{
+		hdr_len = sizeof(struct fch_hdr);
+		fch = skb_push(skb, hdr_len);
+	}
+
+	if(saddr)
+		memcpy(fch->saddr,saddr,dev->addr_len);
+	else
+		memcpy(fch->saddr,dev->dev_addr,dev->addr_len);
+
+	if(daddr)
+	{
+		memcpy(fch->daddr,daddr,dev->addr_len);
+		return hdr_len;
+	}
+	return -hdr_len;
+}
+
+static const struct header_ops fc_header_ops = {
+	.create	 = fc_header,
+};
+
+static void fc_setup(struct net_device *dev)
+{
+	dev->header_ops		= &fc_header_ops;
+	dev->type		= ARPHRD_IEEE802;
+	dev->hard_header_len	= FC_HLEN;
+	dev->mtu		= 2024;
+	dev->addr_len		= FC_ALEN;
+	dev->tx_queue_len	= 100; /* Long queues on fc */
+	dev->flags		= IFF_BROADCAST;
+
+	memset(dev->broadcast, 0xFF, FC_ALEN);
+}
+
+/**
+ * alloc_fcdev - Register fibre channel device
+ * @sizeof_priv: Size of additional driver-private structure to be allocated
+ *	for this fibre channel device
+ *
+ * Fill in the fields of the device structure with fibre channel-generic values.
+ *
+ * Constructs a new net device, complete with a private data area of
+ * size @sizeof_priv.  A 32-byte (not bit) alignment is enforced for
+ * this private data area.
+ */
+struct net_device *alloc_fcdev(int sizeof_priv)
+{
+	return alloc_netdev(sizeof_priv, "fc%d", NET_NAME_UNKNOWN, fc_setup);
+}
+EXPORT_SYMBOL(alloc_fcdev);