staging: comedi: comedi_fops: cast the cmd->chanlist to the correct address space

Rename 'chanlist_saver' to 'user_chanlist' to avoid confusion that
it's actually a __user *.

The chanlist pointer in comedi_cmd is still a user space pointer when
the comedi_cmd is copied with copy_from_user() in do_cmd_ioctl() and
do_cmdtest_ioctl(). This pointer needs to be cast when it is saved in
user_chanlist in order to preserve its address space.

The copy_from_user() call to copy the chanlist to the kernel space
comedi_command requires the second parameter to be a __user pointer.
Use the correctly cast user_chanlist instead of cmd->chanlist.

Before the comedi_cmd is copied back to user space, the saved
user_chanlist pointer is restored. Cast the user_chanlist again so
that the address space matches the comedi_cmd.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index df627c8223d..626fa723f19 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1137,14 +1137,14 @@ static int do_cmd_ioctl(struct comedi_device *dev,
         struct comedi_subdevice *s;
         struct comedi_async *async;
         int ret = 0;
-        unsigned int __user *chanlist_saver = NULL;
+        unsigned int __user *user_chanlist;
 
         if (copy_from_user(&cmd, arg, sizeof(struct comedi_cmd))) {
                 DPRINTK("bad cmd address\n");
                 return -EFAULT;
         }
         /* save user's chanlist pointer so it can be restored later */
-        chanlist_saver = cmd.chanlist;
+        user_chanlist = (unsigned int __user *)cmd.chanlist;
 
         if (cmd.subdev >= dev->n_subdevices) {
                 DPRINTK("%d no such subdevice\n", cmd.subdev);
@@ -1206,7 +1206,7 @@ static int do_cmd_ioctl(struct comedi_device *dev,
                 goto cleanup;
         }
 
-        if (copy_from_user(async->cmd.chanlist, cmd.chanlist,
+        if (copy_from_user(async->cmd.chanlist, user_chanlist,
                            async->cmd.chanlist_len * sizeof(int))) {
                 DPRINTK("fault reading chanlist\n");
                 ret = -EFAULT;
@@ -1228,7 +1228,7 @@ static int do_cmd_ioctl(struct comedi_device *dev,
                 DPRINTK("test returned %d\n", ret);
                 cmd = async->cmd;
                 /* restore chanlist pointer before copying back */
-                cmd.chanlist = chanlist_saver;
+                cmd.chanlist = (unsigned int __force *)user_chanlist;
                 cmd.data = NULL;
                 if (copy_to_user(arg, &cmd, sizeof(struct comedi_cmd))) {
                         DPRINTK("fault writing cmd\n");
@@ -1287,14 +1287,14 @@ static int do_cmdtest_ioctl(struct comedi_device *dev,
         struct comedi_subdevice *s;
         int ret = 0;
         unsigned int *chanlist = NULL;
-        unsigned int __user *chanlist_saver = NULL;
+        unsigned int __user *user_chanlist;
 
         if (copy_from_user(&cmd, arg, sizeof(struct comedi_cmd))) {
                 DPRINTK("bad cmd address\n");
                 return -EFAULT;
         }
         /* save user's chanlist pointer so it can be restored later */
-        chanlist_saver = cmd.chanlist;
+        user_chanlist = (unsigned int __user *)cmd.chanlist;
 
         if (cmd.subdev >= dev->n_subdevices) {
                 DPRINTK("%d no such subdevice\n", cmd.subdev);
@@ -1331,7 +1331,7 @@ static int do_cmdtest_ioctl(struct comedi_device *dev,
                         goto cleanup;
                 }
 
-                if (copy_from_user(chanlist, cmd.chanlist,
+                if (copy_from_user(chanlist, user_chanlist,
                                    cmd.chanlist_len * sizeof(int))) {
                         DPRINTK("fault reading chanlist\n");
                         ret = -EFAULT;
@@ -1351,7 +1351,7 @@ static int do_cmdtest_ioctl(struct comedi_device *dev,
         ret = s->do_cmdtest(dev, s, &cmd);
 
         /* restore chanlist pointer before copying back */
-        cmd.chanlist = chanlist_saver;
+        cmd.chanlist = (unsigned int __force *)user_chanlist;
 
         if (copy_to_user(arg, &cmd, sizeof(struct comedi_cmd))) {
                 DPRINTK("bad cmd address\n");