Messages in this thread | | | Date | Tue, 28 Jan 2014 12:07:51 +0100 (CET) | From | Jiri Kosina <> | Subject | Re: fanotify use after free. |
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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.
-- Jiri Kosina SUSE Labs
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