Bug 13309 - Fix winbind child process exit bug
Fix winbind child process exit bug
Status: ASSIGNED
Product: Samba 4.1 and newer
Classification: Unclassified
Component: Winbind
4.8.0rc2
All All
: P5 normal
: ---
Assigned To: Andreas Schneider
Samba QA Contact
:
Depends on:
Blocks:
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Reported: 2018-02-27 15:49 UTC by Andreas Schneider
Modified: 2019-01-04 08:51 UTC (History)
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Description Andreas Schneider 2018-02-27 15:49:10 UTC
Fix a bug when a child dies when a request is pending in the child. If the     signal handler fires before epoll finds out the other end of the parent-child     socket is closed, we close the socket on our side without taking care of the     pending request. This causes two problems: First, that one pending request     never is replied to properly, and secondly, we might end up with EPOLL_DEL on a     wrong file descriptor. This causes all sorts of trouble if we hit an active     one.
    
The fix for this problem is not to close the socket in winbind_child_died().    This however stops an idle child that dies hard from being properly cleaned up.     The fix for that is to add the child->monitor_fde that is set pending only when     no child request is active. This way we can remove the close(sock) in the     signal handler.
Comment 1 Amit Kumar 2019-01-04 08:51:19 UTC
epoll is monitoring descriptors and associated events 
Signal recieved and signal handler fires(which signal SIGCHLD?) and closes 1 end of named pipe/fifo (may be read or write)
And we close other end.

Can we reproduce this issue, how?

struct winbindd_child {
	..
	int monitor_fde;
};
if (no_child_active)
	monitor_fde=-1;	//pending