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, 126 insertions, 0 deletions

diff --git a/drivers/remoteproc/remoteproc_cdev.c b/drivers/remoteproc/remoteproc_cdev.c
new file mode 100644
index 000000000..687f205fd
--- /dev/null
+++ b/drivers/remoteproc/remoteproc_cdev.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Character device interface driver for Remoteproc framework.
+ *
+ * Copyright (c) 2020, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/cdev.h>
+#include <linux/compat.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/remoteproc.h>
+#include <linux/uaccess.h>
+#include <uapi/linux/remoteproc_cdev.h>
+
+#include "remoteproc_internal.h"
+
+#define NUM_RPROC_DEVICES	64
+static dev_t rproc_major;
+
+static ssize_t rproc_cdev_write(struct file *filp, const char __user *buf, size_t len, loff_t *pos)
+{
+	struct rproc *rproc = container_of(filp->f_inode->i_cdev, struct rproc, cdev);
+	int ret = 0;
+	char cmd[10];
+
+	if (!len || len > sizeof(cmd))
+		return -EINVAL;
+
+	ret = copy_from_user(cmd, buf, len);
+	if (ret)
+		return -EFAULT;
+
+	if (!strncmp(cmd, "start", len)) {
+		ret = rproc_boot(rproc);
+	} else if (!strncmp(cmd, "stop", len)) {
+		ret = rproc_shutdown(rproc);
+	} else if (!strncmp(cmd, "detach", len)) {
+		ret = rproc_detach(rproc);
+	} else {
+		dev_err(&rproc->dev, "Unrecognized option\n");
+		ret = -EINVAL;
+	}
+
+	return ret ? ret : len;
+}
+
+static long rproc_device_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
+{
+	struct rproc *rproc = container_of(filp->f_inode->i_cdev, struct rproc, cdev);
+	void __user *argp = (void __user *)arg;
+	s32 param;
+
+	switch (ioctl) {
+	case RPROC_SET_SHUTDOWN_ON_RELEASE:
+		if (copy_from_user(&param, argp, sizeof(s32)))
+			return -EFAULT;
+
+		rproc->cdev_put_on_release = !!param;
+		break;
+	case RPROC_GET_SHUTDOWN_ON_RELEASE:
+		param = (s32)rproc->cdev_put_on_release;
+		if (copy_to_user(argp, &param, sizeof(s32)))
+			return -EFAULT;
+
+		break;
+	default:
+		dev_err(&rproc->dev, "Unsupported ioctl\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int rproc_cdev_release(struct inode *inode, struct file *filp)
+{
+	struct rproc *rproc = container_of(inode->i_cdev, struct rproc, cdev);
+	int ret = 0;
+
+	if (!rproc->cdev_put_on_release)
+		return 0;
+
+	if (rproc->state == RPROC_RUNNING)
+		rproc_shutdown(rproc);
+	else if (rproc->state == RPROC_ATTACHED)
+		ret = rproc_detach(rproc);
+
+	return ret;
+}
+
+static const struct file_operations rproc_fops = {
+	.write = rproc_cdev_write,
+	.unlocked_ioctl = rproc_device_ioctl,
+	.compat_ioctl = compat_ptr_ioctl,
+	.release = rproc_cdev_release,
+};
+
+int rproc_char_device_add(struct rproc *rproc)
+{
+	int ret;
+
+	cdev_init(&rproc->cdev, &rproc_fops);
+	rproc->cdev.owner = THIS_MODULE;
+
+	rproc->dev.devt = MKDEV(MAJOR(rproc_major), rproc->index);
+	cdev_set_parent(&rproc->cdev, &rproc->dev.kobj);
+	ret = cdev_add(&rproc->cdev, rproc->dev.devt, 1);
+	if (ret < 0)
+		dev_err(&rproc->dev, "Failed to add char dev for %s\n", rproc->name);
+
+	return ret;
+}
+
+void rproc_char_device_remove(struct rproc *rproc)
+{
+	cdev_del(&rproc->cdev);
+}
+
+void __init rproc_init_cdev(void)
+{
+	int ret;
+
+	ret = alloc_chrdev_region(&rproc_major, 0, NUM_RPROC_DEVICES, "remoteproc");
+	if (ret < 0)
+		pr_err("Failed to alloc rproc_cdev region, err %d\n", ret);
+}