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, 51 insertions, 0 deletions

diff --git a/net/atm/common.h b/net/atm/common.h
new file mode 100644
index 000000000..11cb51dd7
--- /dev/null
+++ b/net/atm/common.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* net/atm/common.h - ATM sockets (common part for PVC and SVC) */
+
+/* Written 1995-2000 by Werner Almesberger, EPFL LRC/ICA */
+
+
+#ifndef NET_ATM_COMMON_H
+#define NET_ATM_COMMON_H
+
+#include <linux/net.h>
+#include <linux/poll.h> /* for poll_table */
+
+
+int vcc_create(struct net *net, struct socket *sock, int protocol, int family, int kern);
+int vcc_release(struct socket *sock);
+int vcc_connect(struct socket *sock, int itf, short vpi, int vci);
+int vcc_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
+		int flags);
+int vcc_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len);
+__poll_t vcc_poll(struct file *file, struct socket *sock, poll_table *wait);
+int vcc_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
+int vcc_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
+int vcc_setsockopt(struct socket *sock, int level, int optname,
+		   sockptr_t optval, unsigned int optlen);
+int vcc_getsockopt(struct socket *sock, int level, int optname,
+		   sockopt_t *opt);
+void vcc_process_recv_queue(struct atm_vcc *vcc);
+
+int atmpvc_init(void);
+void atmpvc_exit(void);
+int atm_sysfs_init(void);
+void atm_sysfs_exit(void);
+
+#ifdef CONFIG_PROC_FS
+int atm_proc_init(void);
+void atm_proc_exit(void);
+#else
+static inline int atm_proc_init(void)
+{
+	return 0;
+}
+
+static inline void atm_proc_exit(void)
+{
+	/* nothing */
+}
+#endif /* CONFIG_PROC_FS */
+
+void atm_dev_release_vccs(struct atm_dev *dev);
+
+#endif