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, 59 insertions, 0 deletions

diff --git a/fs/ext2/xattr_security.c b/fs/ext2/xattr_security.c
new file mode 100644
index 000000000..db47b8ab1
--- /dev/null
+++ b/fs/ext2/xattr_security.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/ext2/xattr_security.c
+ * Handler for storing security labels as extended attributes.
+ */
+
+#include "ext2.h"
+#include <linux/security.h>
+#include "xattr.h"
+
+static int
+ext2_xattr_security_get(const struct xattr_handler *handler,
+			struct dentry *unused, struct inode *inode,
+			const char *name, void *buffer, size_t size)
+{
+	return ext2_xattr_get(inode, EXT2_XATTR_INDEX_SECURITY, name,
+			      buffer, size);
+}
+
+static int
+ext2_xattr_security_set(const struct xattr_handler *handler,
+			struct mnt_idmap *idmap,
+			struct dentry *unused, struct inode *inode,
+			const char *name, const void *value,
+			size_t size, int flags)
+{
+	return ext2_xattr_set(inode, EXT2_XATTR_INDEX_SECURITY, name,
+			      value, size, flags);
+}
+
+static int ext2_initxattrs(struct inode *inode, const struct xattr *xattr_array,
+			   void *fs_info)
+{
+	const struct xattr *xattr;
+	int err = 0;
+
+	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
+		err = ext2_xattr_set(inode, EXT2_XATTR_INDEX_SECURITY,
+				     xattr->name, xattr->value,
+				     xattr->value_len, 0);
+		if (err < 0)
+			break;
+	}
+	return err;
+}
+
+int
+ext2_init_security(struct inode *inode, struct inode *dir,
+		   const struct qstr *qstr)
+{
+	return security_inode_init_security(inode, dir, qstr,
+					    &ext2_initxattrs, NULL);
+}
+
+const struct xattr_handler ext2_xattr_security_handler = {
+	.prefix	= XATTR_SECURITY_PREFIX,
+	.get	= ext2_xattr_security_get,
+	.set	= ext2_xattr_security_set,
+};