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, 70 insertions, 0 deletions

diff --git a/fs/hfsplus/ioctl.c b/fs/hfsplus/ioctl.c
new file mode 100644
index 000000000..40d04dba1
--- /dev/null
+++ b/fs/hfsplus/ioctl.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/hfsplus/ioctl.c
+ *
+ * Copyright (C) 2003
+ * Ethan Benson <erbenson@alaska.net>
+ * partially derived from linux/fs/ext2/ioctl.c
+ * Copyright (C) 1993, 1994, 1995
+ * Remy Card (card@masi.ibp.fr)
+ * Laboratoire MASI - Institut Blaise Pascal
+ * Universite Pierre et Marie Curie (Paris VI)
+ *
+ * hfsplus ioctls
+ */
+
+#include <linux/capability.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/sched.h>
+#include <linux/uaccess.h>
+#include "hfsplus_fs.h"
+
+/*
+ * "Blessing" an HFS+ filesystem writes metadata to the superblock informing
+ * the platform firmware which file to boot from
+ */
+static int hfsplus_ioctl_bless(struct file *file, int __user *user_flags)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	struct inode *inode = d_inode(dentry);
+	struct hfsplus_sb_info *sbi = HFSPLUS_SB(inode->i_sb);
+	struct hfsplus_vh *vh = sbi->s_vhdr;
+	struct hfsplus_vh *bvh = sbi->s_backup_vhdr;
+	u32 cnid = (unsigned long)dentry->d_fsdata;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	mutex_lock(&sbi->vh_mutex);
+
+	/* Directory containing the bootable system */
+	vh->finder_info[0] = bvh->finder_info[0] =
+		cpu_to_be32(d_parent_ino(dentry));
+
+	/*
+	 * Bootloader. Just using the inode here breaks in the case of
+	 * hard links - the firmware wants the ID of the hard link file,
+	 * but the inode points at the indirect inode
+	 */
+	vh->finder_info[1] = bvh->finder_info[1] = cpu_to_be32(cnid);
+
+	/* Per spec, the OS X system folder - same as finder_info[0] here */
+	vh->finder_info[5] = bvh->finder_info[5] =
+		cpu_to_be32(d_parent_ino(dentry));
+
+	mutex_unlock(&sbi->vh_mutex);
+	return 0;
+}
+
+long hfsplus_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	void __user *argp = (void __user *)arg;
+
+	switch (cmd) {
+	case HFSPLUS_IOC_BLESS:
+		return hfsplus_ioctl_bless(file, argp);
+	default:
+		return -ENOTTY;
+	}
+}