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, 222 insertions, 0 deletions

diff --git a/security/apparmor/path.c b/security/apparmor/path.c
new file mode 100644
index 000000000..2494e8101
--- /dev/null
+++ b/security/apparmor/path.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AppArmor security module
+ *
+ * This file contains AppArmor function for pathnames
+ *
+ * Copyright (C) 1998-2008 Novell/SUSE
+ * Copyright 2009-2010 Canonical Ltd.
+ */
+
+#include <linux/magic.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/nsproxy.h>
+#include <linux/path.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/fs_struct.h>
+
+#include "include/apparmor.h"
+#include "include/path.h"
+#include "include/policy.h"
+
+/* modified from dcache.c */
+static int prepend(char **buffer, int buflen, const char *str, int namelen)
+{
+	buflen -= namelen;
+	if (buflen < 0)
+		return -ENAMETOOLONG;
+	*buffer -= namelen;
+	memcpy(*buffer, str, namelen);
+	return 0;
+}
+
+#define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
+
+/* If the path is not connected to the expected root,
+ * check if it is a sysctl and handle specially else remove any
+ * leading / that __d_path may have returned.
+ * Unless
+ *     specifically directed to connect the path,
+ * OR
+ *     if in a chroot and doing chroot relative paths and the path
+ *     resolves to the namespace root (would be connected outside
+ *     of chroot) and specifically directed to connect paths to
+ *     namespace root.
+ */
+static int disconnect(const struct path *path, char *buf, char **name,
+		      int flags, const char *disconnected)
+{
+	int error = 0;
+
+	if (!(flags & PATH_CONNECT_PATH) &&
+	    !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
+	      our_mnt(path->mnt))) {
+		/* disconnected path, don't return pathname starting
+		 * with '/'
+		 */
+		error = -EACCES;
+		if (**name == '/')
+			*name = *name + 1;
+	} else {
+		if (**name != '/')
+			/* CONNECT_PATH with missing root */
+			error = prepend(name, *name - buf, "/", 1);
+		if (!error && disconnected)
+			error = prepend(name, *name - buf, disconnected,
+					strlen(disconnected));
+	}
+
+	return error;
+}
+
+/**
+ * d_namespace_path - lookup a name associated with a given path
+ * @path: path to lookup  (NOT NULL)
+ * @buf:  buffer to store path to  (NOT NULL)
+ * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
+ * @flags: flags controlling path lookup
+ * @disconnected: string to prefix to disconnected paths
+ *
+ * Handle path name lookup.
+ *
+ * Returns: %0 else error code if path lookup fails
+ *          When no error the path name is returned in @name which points to
+ *          a position in @buf
+ */
+static int d_namespace_path(const struct path *path, char *buf, char **name,
+			    int flags, const char *disconnected)
+{
+	char *res;
+	int error = 0;
+	int connected = 1;
+	int isdir = (flags & PATH_IS_DIR) ? 1 : 0;
+	int buflen = aa_g_path_max - isdir;
+
+	if (path->mnt->mnt_flags & MNT_INTERNAL) {
+		/* it's not mounted anywhere */
+		res = dentry_path(path->dentry, buf, buflen);
+		*name = res;
+		if (IS_ERR(res)) {
+			*name = buf;
+			return PTR_ERR(res);
+		}
+		if (path->dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
+		    strncmp(*name, "/sys/", 5) == 0) {
+			/* TODO: convert over to using a per namespace
+			 * control instead of hard coded /proc
+			 */
+			error = prepend(name, *name - buf, "/proc", 5);
+			goto out;
+		} else
+			error = disconnect(path, buf, name, flags,
+					   disconnected);
+		goto out;
+	}
+
+	/* resolve paths relative to chroot?*/
+	if (flags & PATH_CHROOT_REL) {
+		struct path root;
+		get_fs_root(current->fs, &root);
+		res = __d_path(path, &root, buf, buflen);
+		path_put(&root);
+	} else {
+		res = d_absolute_path(path, buf, buflen);
+		if (!our_mnt(path->mnt))
+			connected = 0;
+	}
+
+	/* handle error conditions - and still allow a partial path to
+	 * be returned.
+	 */
+	if (IS_ERR_OR_NULL(res)) {
+		if (PTR_ERR(res) == -ENAMETOOLONG) {
+			error = -ENAMETOOLONG;
+			*name = buf;
+			goto out;
+		}
+		connected = 0;
+		res = dentry_path_raw(path->dentry, buf, buflen);
+		if (IS_ERR(res)) {
+			error = PTR_ERR(res);
+			*name = buf;
+			goto out;
+		}
+	} else if (!our_mnt(path->mnt))
+		connected = 0;
+
+	*name = res;
+
+	if (!connected)
+		error = disconnect(path, buf, name, flags, disconnected);
+
+	/* Handle two cases:
+	 * 1. A deleted dentry && profile is not allowing mediation of deleted
+	 * 2. On some filesystems, newly allocated dentries appear to the
+	 *    security_path hooks as a deleted dentry except without an inode
+	 *    allocated.
+	 */
+	if (d_unlinked(path->dentry) && d_is_positive(path->dentry) &&
+	    !(flags & (PATH_MEDIATE_DELETED | PATH_DELEGATE_DELETED))) {
+			error = -ENOENT;
+			goto out;
+	}
+
+out:
+	/* Append "/" to directory paths and reterminate string, except for
+	 * root "/" which already ends in a slash.
+	 */
+	if (!error && isdir) {
+		bool is_root = (*name)[0] == '/' && (*name)[1] == '\0';
+
+		if (!is_root) {
+			buf[aa_g_path_max - 2] = '/';
+			buf[aa_g_path_max - 1] = '\0';
+		}
+	}
+
+	return error;
+}
+
+/**
+ * aa_path_name - get the pathname to a buffer ensure dir / is appended
+ * @path: path the file  (NOT NULL)
+ * @flags: flags controlling path name generation
+ * @buffer: buffer to put name in (NOT NULL)
+ * @name: Returns - the generated path name if !error (NOT NULL)
+ * @info: Returns - information on why the path lookup failed (MAYBE NULL)
+ * @disconnected: string to prepend to disconnected paths
+ *
+ * @name is a pointer to the beginning of the pathname (which usually differs
+ * from the beginning of the buffer), or NULL.  If there is an error @name
+ * may contain a partial or invalid name that can be used for audit purposes,
+ * but it can not be used for mediation.
+ *
+ * We need PATH_IS_DIR to indicate whether the file is a directory or not
+ * because the file may not yet exist, and so we cannot check the inode's
+ * file type.
+ *
+ * Returns: %0 else error code if could retrieve name
+ */
+int aa_path_name(const struct path *path, int flags, char *buffer,
+		 const char **name, const char **info, const char *disconnected)
+{
+	char *str = NULL;
+	int error = d_namespace_path(path, buffer, &str, flags, disconnected);
+
+	if (info && error) {
+		if (error == -ENOENT)
+			*info = "Failed name lookup - deleted entry";
+		else if (error == -EACCES)
+			*info = "Failed name lookup - disconnected path";
+		else if (error == -ENAMETOOLONG)
+			*info = "Failed name lookup - name too long";
+		else
+			*info = "Failed name lookup";
+	}
+
+	*name = str;
+
+	return error;
+}