Messages in this thread | | | Subject | Re: [PATCH] xfs: fix use-after-free on CIL context on shutdown | From | "yukuai (C)" <> | Date | Tue, 16 Jun 2020 09:16:09 +0800 |
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On 2020/6/11 10:45, Dave Chinner wrote: > > From: Dave Chinner <dchinner@redhat.com> > > xlog_wait() on the CIL context can reference a freed context if the > waiter doesn't get scheduled before the CIL context is freed. This > can happen when a task is on the hard throttle and the CIL push > aborts due to a shutdown. This was detected by generic/019: > > thread 1 thread 2 > > __xfs_trans_commit > xfs_log_commit_cil > <CIL size over hard throttle limit> > xlog_wait > schedule > xlog_cil_push_work > wake_up_all > <shutdown aborts commit> > xlog_cil_committed > kmem_free > > remove_wait_queue > spin_lock_irqsave --> UAF > > Fix it by moving the wait queue to the CIL rather than keeping it in > in the CIL context that gets freed on push completion. Because the > wait queue is now independent of the CIL context and we might have > multiple contexts in flight at once, only wake the waiters on the > push throttle when the context we are pushing is over the hard > throttle size threshold.
Hi, Dave,
How do you think about the following fix:
1. use autoremove_wake_func(), and remove remove_wait_queue() to avoid UAF. 2. add finish_wait().
@@ -576,12 +576,13 @@ xlog_wait( __releases(lock) { DECLARE_WAITQUEUE(wait, current); + wait.func = autoremove_wake_function;
add_wait_queue_exclusive(wq, &wait); __set_current_state(TASK_UNINTERRUPTIBLE); spin_unlock(lock); schedule(); - remove_wait_queue(wq, &wait); + finish_wait(wq, &wait); }
Best regards! Yu Kuai
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