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Date: Tue, 27 Oct 2015 16:12:50 -0400 From: Jean-François Dagenais <jeff.dagenais@...il.com> To: Brian Russell <brussell@...cade.com> Cc: Guenter Roeck <linux@...ck-us.net>, Brian Russell <brian.russell@...cade.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Hans J. Koch" <hjk@...sjkoch.de>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v9 2/2] uio: Fix uio driver to refcount device Hi guys, We have hot-removal scenarios here which require exactly this fix. The app above has open fds on /dev/uioN and the current uio.c makes the kernel OOPS. Any updates? I'd be happy to test a new patch. On Mon, Jun 8, 2015 at 4:07 PM, Brian Russell <brussell@...cade.com> wrote: > >> On 8 Jun 2015, at 20:25, Guenter Roeck <linux@...ck-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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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