On Tue, Jan 28, 2014 at 03:53:27PM +0100, Jan Kara wrote:
> On Tue 28-01-14 12:07:51, Jiri Kosina wrote:
> > On Tue, 28 Jan 2014, Jan Kara wrote:
> >
> > > > 2b:* 4d 8b 64 c6 08 mov 0x8(%r14,%rax,8),%r12 <--
> > > > trapping instruction
> > > >
> > > > R14 is 0x6b6b6b6b6b6b6c03, which looks like a use-after-free.
> > > Yup. But I'm somewhat puzzled by the trace. We crash when calling
> > > fsnotify_destroy_event() from fanotify_handle_event(). The fsnotify code
> > > has been called from do_sys_open() so the event was a 'FS_OPEN' which
> > > fails
> > > the fsn_event->mask & FAN_ALL_PERM_EVENTS test.
> > >
> > > Slapping my forehead, that's a really stupid bug. The event
> > > fsnotify_add_notify_event() returns may be freed by the time we return
> > > because we already dropped the notification mutex. And then
> > > fsn_event->mask
> > > & FAN_ALL_PERM_EVENTS test will pass because FAN_ALL_PERM_EVENTS matches
> > > with the poison pattern 0x6b6b6b6b. So yet another hacked up version of
> > > fanotify fix is attached. And I have to seriously think about use counts
> > > for fanotify version of that struct.
> >
> > With the fixed version of the patch, all the fanotify-related oopses are
> > gone on my system.
> Thanks for testing. So now I have to come up with something mergeable :)
Yep, looks good to me too. Thanks.
Dave
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