Messages in this thread | | | Date | Sat, 29 Mar 2008 13:20:10 +0100 | From | Björn Steinbrink <> | Subject | Re: Oops/Warning report for the week of March 28th 2008 |
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On 2008.03.28 17:16:42 -0400, Dmitry Torokhov wrote: > On Fri, Mar 28, 2008 at 01:51:38PM -0700, Linus Torvalds wrote: > > > > > > On Fri, 28 Mar 2008, Linus Torvalds wrote: > > > > > > Is there something obvious that I'm missing? I'd really like to see the > > > whole posting that the oops came from. Do you save the originals or even > > > just message ID's from the ones you pick from emails? > > > > Hmm. Definitely not from the kernel mailing list. I'm intrigued, where did > > that oops #5814 come from (picked a recent one at random)? > > > > The thing is recent, and oopses on "mutex_lock(dev->mutex)" in > > input_release_device. In particular, the path *seems* to be this one: > > > > evdev_release -> > > evdev_ungrab -> > > input_release_device -> > > mutex_lock -> > > mutex_lock_nested -> > > __mutex_lock_common -> > > list_add_tail(&waiter.list, &lock->wait_list) > > > > where "lock->wait_list.prev" seems to be 0x6b6b6b6b6b6b6b6b, which is the > > use-after-free poison pattern. > > > > (In fact, I think the access that actually oopses is when the > > debug version of __list_add() does > > > > if (unlikely(prev->next != next)) { > > > > because that "prev" pointer is crap). > > > > So it seems that when input_release_device() does: > > > > struct input_dev *dev = handle->dev; > > > > mutex_lock(&dev->mutex); > > > > the "dev" it uses has already been released. And this only shows up as a > > problem when you have slab debugging turned on (like the Fedora kernels > > do, thank you all Fedora guys). > > > > The odd thing is that I don't think any of this code has really changed > > recently. > > > > There is a patch from Pete that works around the problem by not > calling input_release_device() on devices that are gone. But what > I don't understand is why the parent input device is gone since > sysfs/driver core should be keeping a reference to it since it is > a parent of evdev. input_dev shoudl only be released after > evdev_free() is called.
Hm? evdev_free only does the final kfree call. The calls to device_del and put_device are already happening in device_disconnect, so the parent can go away any time after that. Do you say that that should be moved into evdev_free instead? I'm not familiar with the code, but at first sight, I'd say that we should have a "if (evdev->grab) evdev_ungrab(evdev, evdev->grab)" in evdev_cleanup, looks like the logical place to do that. Anything I'm missing?
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