David Miller <da...@davemloft.net> writes: > From: Jason Baron <jba...@akamai.com> > Date: Fri, 9 Oct 2015 00:15:59 -0400 > >> These patches are against mainline, I can re-base to net-next, please >> let me know. >> >> They have been tested against: https://lkml.org/lkml/2015/9/13/195, >> which causes the use-after-free quite quickly and here: >> https://lkml.org/lkml/2015/10/2/693. > > I'd like to understand how patches that don't even compile can be > "tested"? > > net/unix/af_unix.c: In function ‘unix_dgram_writable’: > net/unix/af_unix.c:2480:3: error: ‘other_full’ undeclared (first use in this > function) > net/unix/af_unix.c:2480:3: note: each undeclared identifier is reported only > once for each function it appears in > > Could you explain how that works, I'm having a hard time understanding > this?
This is basicallly a workaround for the problem that it's not possible to tell epoll to let go of a certain wait queue: Instead of registering the peer_wait queue via sock_poll_wait, a wait_queue_t under control of the af_unix.c code is linked onto it which relays a wake up on the peer_wait queue to the 'ordinary' wait queue associated with the polled socket via custom wake function. But (at least the code I looked it) it enqueues a unix socket on connect which has certain side effects (in particular, /dev/log will have a seriously large wait queue of entirely uninterested peers) and in many cases, this is simply not necessary, as the additional peer_wait event is only interesting in case a peer of a fan-in socket (like /dev/log) happens to be waiting for writeabilty via poll/ select/ epoll/ ... Since the wait queue handling code is now under control of the af_unix.c code, it can remove itself from the peer_wait queue prior to dropping its reference to a peer on disconnect or on detecting a dead peer in unix_dgram_sendmsg. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
