Messages in this thread |  | | From | Brian Russell <> | Subject | Re: [PATCH v9 2/2] uio: Fix uio driver to refcount device | Date | Mon, 8 Jun 2015 21:07:30 +0100 |
| |
> On 8 Jun 2015, at 20:25, Guenter Roeck <linux@roeck-us.net> wrote: > >> On Tue, Mar 24, 2015 at 12:59:22PM +0000, Brian Russell wrote: >> >> >>> On 23/03/15 20:41, Greg Kroah-Hartman wrote: >>>> On Fri, Mar 20, 2015 at 02:54:44PM +0000, Brian Russell wrote: >>>> Protect uio driver from its owner being unplugged while there are open fds. >>>> Embed struct device in struct uio_device, use refcounting on device, free >>>> uio_device on release. >>>> info struct passed in uio_register_device can be freed on unregister, so null >>>> out the field in uio_unregister_device and check accesses. >>> >>> That's really not protecting anything except heavy-handed problems... >>> >>> Look at the code: >>> >>>> @@ -493,7 +499,7 @@ static unsigned int uio_poll(struct file *filep, poll_table *wait) >>>> struct uio_listener *listener = filep->private_data; >>>> struct uio_device *idev = listener->dev; >>>> >>>> - if (!idev->info->irq) >>>> + if (!idev->info || !idev->info->irq) >>>> return -EIO; >>> >>> Great, you checked the irq value, but what if it changes the very next >>> line: >>> >>>> poll_wait(filep, &idev->wait, wait); >>> >>> Or any other line within this function? Or any other function that you >>> try to check the value for in the beginning... >>> >>> This really isn't protecting anything "properly", sorry. Either we >>> don't care about it (hint, I don't think we really do), or we need to >>> properly lock things and check, and protect, things that way. >> >> The checks for irq value are already there. I added the checks for the >> idev->info ptr and deliberately nulled it in uio_unregister_device as >> the caller module may free uio_info after unregistering (dpdk's igb_uio >> does anyway) and then release will be called later when fds are closed. >> >> So I think I definitely need the check in uio_release. I didn't think >> it hurt to return early from poll/read/write if we know the device >> has been unregistered? > > What is the final verdict on this patch ? We are seeing the crash in our > system, and I would like to apply a 'final' patch if possible to get it > fixed. > It needs a bit more work. uio_info needs to live as long as the corresponding uio_device. Since they seem to always be 1:1, uio_info could embedded within uio_device (but then all the users of uio need changed) or uio_info could be a refcounted object.
Brian
> Thanks, > Guenter
|  |