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, 162 insertions, 0 deletions

diff --git a/net/atm/pvc.c b/net/atm/pvc.c
new file mode 100644
index 000000000..8b2c3e515
--- /dev/null
+++ b/net/atm/pvc.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0
+/* net/atm/pvc.c - ATM PVC sockets */
+
+/* Written 1995-2000 by Werner Almesberger, EPFL LRC/ICA */
+
+
+#include <linux/net.h>		/* struct socket, struct proto_ops */
+#include <linux/atm.h>		/* ATM stuff */
+#include <linux/atmdev.h>	/* ATM devices */
+#include <linux/errno.h>	/* error codes */
+#include <linux/kernel.h>	/* printk */
+#include <linux/init.h>
+#include <linux/skbuff.h>
+#include <linux/bitops.h>
+#include <linux/export.h>
+#include <net/sock.h>		/* for sock_no_* */
+
+#include "resources.h"		/* devs and vccs */
+#include "common.h"		/* common for PVCs and SVCs */
+
+
+static int pvc_shutdown(struct socket *sock, int how)
+{
+	return 0;
+}
+
+static int pvc_bind(struct socket *sock, struct sockaddr_unsized *sockaddr,
+		    int sockaddr_len)
+{
+	struct sock *sk = sock->sk;
+	struct sockaddr_atmpvc *addr;
+	struct atm_vcc *vcc;
+	int error;
+
+	if (sockaddr_len != sizeof(struct sockaddr_atmpvc))
+		return -EINVAL;
+	addr = (struct sockaddr_atmpvc *)sockaddr;
+	if (addr->sap_family != AF_ATMPVC)
+		return -EAFNOSUPPORT;
+	lock_sock(sk);
+	vcc = ATM_SD(sock);
+	if (!test_bit(ATM_VF_HASQOS, &vcc->flags)) {
+		error = -EBADFD;
+		goto out;
+	}
+	if (test_bit(ATM_VF_PARTIAL, &vcc->flags)) {
+		if (vcc->vpi != ATM_VPI_UNSPEC)
+			addr->sap_addr.vpi = vcc->vpi;
+		if (vcc->vci != ATM_VCI_UNSPEC)
+			addr->sap_addr.vci = vcc->vci;
+	}
+	error = vcc_connect(sock, addr->sap_addr.itf, addr->sap_addr.vpi,
+			    addr->sap_addr.vci);
+out:
+	release_sock(sk);
+	return error;
+}
+
+static int pvc_connect(struct socket *sock, struct sockaddr_unsized *sockaddr,
+		       int sockaddr_len, int flags)
+{
+	return pvc_bind(sock, sockaddr, sockaddr_len);
+}
+
+static int pvc_setsockopt(struct socket *sock, int level, int optname,
+			  sockptr_t optval, unsigned int optlen)
+{
+	struct sock *sk = sock->sk;
+	int error;
+
+	lock_sock(sk);
+	error = vcc_setsockopt(sock, level, optname, optval, optlen);
+	release_sock(sk);
+	return error;
+}
+
+static int pvc_getsockopt(struct socket *sock, int level, int optname,
+			  sockopt_t *opt)
+{
+	struct sock *sk = sock->sk;
+	int error;
+
+	lock_sock(sk);
+	error = vcc_getsockopt(sock, level, optname, opt);
+	release_sock(sk);
+	return error;
+}
+
+static int pvc_getname(struct socket *sock, struct sockaddr *sockaddr,
+		       int peer)
+{
+	struct sockaddr_atmpvc *addr;
+	struct atm_vcc *vcc = ATM_SD(sock);
+
+	if (!vcc->dev || !test_bit(ATM_VF_ADDR, &vcc->flags))
+		return -ENOTCONN;
+	addr = (struct sockaddr_atmpvc *)sockaddr;
+	memset(addr, 0, sizeof(*addr));
+	addr->sap_family = AF_ATMPVC;
+	addr->sap_addr.itf = vcc->dev->number;
+	addr->sap_addr.vpi = vcc->vpi;
+	addr->sap_addr.vci = vcc->vci;
+	return sizeof(struct sockaddr_atmpvc);
+}
+
+static const struct proto_ops pvc_proto_ops = {
+	.family =	PF_ATMPVC,
+	.owner =	THIS_MODULE,
+
+	.release =	vcc_release,
+	.bind =		pvc_bind,
+	.connect =	pvc_connect,
+	.socketpair =	sock_no_socketpair,
+	.accept =	sock_no_accept,
+	.getname =	pvc_getname,
+	.poll =		vcc_poll,
+	.ioctl =	vcc_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = vcc_compat_ioctl,
+#endif
+	.gettstamp =	sock_gettstamp,
+	.listen =	sock_no_listen,
+	.shutdown =	pvc_shutdown,
+	.setsockopt =	pvc_setsockopt,
+	.getsockopt_iter = pvc_getsockopt,
+	.sendmsg =	vcc_sendmsg,
+	.recvmsg =	vcc_recvmsg,
+	.mmap =		sock_no_mmap,
+};
+
+
+static int pvc_create(struct net *net, struct socket *sock, int protocol,
+		      int kern)
+{
+	if (net != &init_net)
+		return -EAFNOSUPPORT;
+
+	sock->ops = &pvc_proto_ops;
+	return vcc_create(net, sock, protocol, PF_ATMPVC, kern);
+}
+
+static const struct net_proto_family pvc_family_ops = {
+	.family = PF_ATMPVC,
+	.create = pvc_create,
+	.owner = THIS_MODULE,
+};
+
+
+/*
+ *	Initialize the ATM PVC protocol family
+ */
+
+
+int __init atmpvc_init(void)
+{
+	return sock_register(&pvc_family_ops);
+}
+
+void atmpvc_exit(void)
+{
+	sock_unregister(PF_ATMPVC);
+}