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? Thanks, Brian > Please do the first one, as the reference count should be all that we > need to care about here. > > Sorry I missed this on the previous review, just realized it now this > time around. > > thanks, > > greg k-h > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
