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, 69 insertions, 0 deletions

diff --git a/security/integrity/integrity_audit.c b/security/integrity/integrity_audit.c
new file mode 100644
index 000000000..d8d9e5ff1
--- /dev/null
+++ b/security/integrity/integrity_audit.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2008 IBM Corporation
+ * Author: Mimi Zohar <zohar@us.ibm.com>
+ *
+ * File: integrity_audit.c
+ *	Audit calls for the integrity subsystem
+ */
+
+#include <linux/fs.h>
+#include <linux/gfp.h>
+#include <linux/audit.h>
+#include "integrity.h"
+
+static int integrity_audit_info;
+
+/* ima_audit_setup - enable informational auditing messages */
+static int __init integrity_audit_setup(char *str)
+{
+	unsigned long audit;
+
+	if (!kstrtoul(str, 0, &audit))
+		integrity_audit_info = audit ? 1 : 0;
+	return 1;
+}
+__setup("integrity_audit=", integrity_audit_setup);
+
+void integrity_audit_msg(int audit_msgno, struct inode *inode,
+			 const unsigned char *fname, const char *op,
+			 const char *cause, int result, int audit_info)
+{
+	integrity_audit_message(audit_msgno, inode, fname, op, cause,
+				result, audit_info, 0);
+}
+
+void integrity_audit_message(int audit_msgno, struct inode *inode,
+			     const unsigned char *fname, const char *op,
+			     const char *cause, int result, int audit_info,
+			     int errno)
+{
+	struct audit_buffer *ab;
+	char name[TASK_COMM_LEN];
+
+	if (!integrity_audit_info && audit_info == 1)	/* Skip info messages */
+		return;
+
+	ab = audit_log_start(audit_context(), GFP_KERNEL, audit_msgno);
+	if (!ab)
+		return;
+	audit_log_format(ab, "pid=%d uid=%u auid=%u ses=%u",
+			 task_pid_nr(current),
+			 from_kuid(&init_user_ns, current_uid()),
+			 from_kuid(&init_user_ns, audit_get_loginuid(current)),
+			 audit_get_sessionid(current));
+	audit_log_task_context(ab);
+	audit_log_format(ab, " op=%s cause=%s comm=", op, cause);
+	audit_log_untrustedstring(ab, get_task_comm(name, current));
+	if (fname) {
+		audit_log_format(ab, " name=");
+		audit_log_untrustedstring(ab, fname);
+	}
+	if (inode) {
+		audit_log_format(ab, " dev=");
+		audit_log_untrustedstring(ab, inode->i_sb->s_id);
+		audit_log_format(ab, " ino=%llu", inode->i_ino);
+	}
+	audit_log_format(ab, " res=%d errno=%d", !result, errno);
+	audit_log_end(ab);
+}