| From abbotti@mev.co.uk Fri Mar 1 11:20:18 2013 |
| From: Ian Abbott <abbotti@mev.co.uk> |
| Date: Wed, 27 Feb 2013 10:56:19 +0000 |
| Subject: staging: comedi: check s->async for poll(), read() and write() |
| To: stable@vger.kernel.org |
| Cc: gregkh@linuxfoundation.org, Ian Abbott <abbotti@mev.co.uk> |
| Message-ID: <1361962579-4790-1-git-send-email-abbotti@mev.co.uk> |
| |
| From: Ian Abbott <abbotti@mev.co.uk> |
| |
| commit cc400e185c07c15a42d2635995f422de5b94b696 upstream. |
| |
| Some low-level comedi drivers (incorrectly) point `dev->read_subdev` or |
| `dev->write_subdev` to a subdevice that does not support asynchronous |
| commands. Comedi's poll(), read() and write() file operation handlers |
| assume these subdevices do support asynchronous commands. In |
| particular, they assume `s->async` is valid (where `s` points to the |
| read or write subdevice), which it won't be if it has been set |
| incorrectly. This can lead to a NULL pointer dereference. |
| |
| Check `s->async` is non-NULL in `comedi_poll()`, `comedi_read()` and |
| `comedi_write()` to avoid the bug. |
| |
| Signed-off-by: Ian Abbott <abbotti@mev.co.uk> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/staging/comedi/comedi_fops.c | 8 ++++---- |
| 1 file changed, 4 insertions(+), 4 deletions(-) |
| |
| --- a/drivers/staging/comedi/comedi_fops.c |
| +++ b/drivers/staging/comedi/comedi_fops.c |
| @@ -1577,7 +1577,7 @@ static unsigned int comedi_poll(struct f |
| |
| mask = 0; |
| read_subdev = comedi_get_read_subdevice(dev_file_info); |
| - if (read_subdev) { |
| + if (read_subdev && read_subdev->async) { |
| poll_wait(file, &read_subdev->async->wait_head, wait); |
| if (!read_subdev->busy |
| || comedi_buf_read_n_available(read_subdev->async) > 0 |
| @@ -1587,7 +1587,7 @@ static unsigned int comedi_poll(struct f |
| } |
| } |
| write_subdev = comedi_get_write_subdevice(dev_file_info); |
| - if (write_subdev) { |
| + if (write_subdev && write_subdev->async) { |
| poll_wait(file, &write_subdev->async->wait_head, wait); |
| comedi_buf_write_alloc(write_subdev->async, |
| write_subdev->async->prealloc_bufsz); |
| @@ -1629,7 +1629,7 @@ static ssize_t comedi_write(struct file |
| } |
| |
| s = comedi_get_write_subdevice(dev_file_info); |
| - if (s == NULL) { |
| + if (s == NULL || s->async == NULL) { |
| retval = -EIO; |
| goto done; |
| } |
| @@ -1740,7 +1740,7 @@ static ssize_t comedi_read(struct file * |
| } |
| |
| s = comedi_get_read_subdevice(dev_file_info); |
| - if (s == NULL) { |
| + if (s == NULL || s->async == NULL) { |
| retval = -EIO; |
| goto done; |
| } |