[patch] potential race in epoll_ctl(EPOLL_CTL_MOD) ...

[Davide Libenzi]

Andrew, a potential race can happen in epoll_ctl(EPOLL_CTL_MOD) where an 
event can happen in between f_op->poll() and the lock on ep->lock (we 
cannot call f_op->poll() inside a lock, and the f_op->poll() callback does 
not carry any info at the current time - missing wake_up_info() already ;).
In that case the event would be removed. We can easily leave the event 
inside the ready list and have the ep_send_events() logic do the job for 
us at later time.
(Thanks to david.lee@xxxxxxxxxxxx for reporting the thing, since it 
shouldn't have been a nice one ;)



- Davide




--- a/fs/eventpoll.c	2004-02-13 14:13:29.417933600 -0800
+++ b/fs/eventpoll.c	2004-02-13 14:13:46.999260832 -0800
@@ -1155,8 +1155,7 @@
 				if (waitqueue_active(&ep->poll_wait))
 					pwake++;
 			}
-		} else if (EP_IS_LINKED(&epi->rdllink))
-			EP_LIST_DEL(&epi->rdllink);
+		}
 	}
 
 	write_unlock_irqrestore(&ep->lock, flags);







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