Messages in this thread | | | Date | Tue, 28 Jan 2014 10:24:08 -0500 | From | Dave Jones <> | Subject | Re: fanotify use after free. |
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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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