Messages in this thread | | | Subject | Re: [PATCH] net, socket, socket_wq: fix missing initialization of flags | From | Eric Dumazet <> | Date | Mon, 28 Dec 2015 12:19:46 -0500 |
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On Sun, 2015-12-27 at 21:00 +0100, Nicolai Stange wrote: > Fixes: ceb5d58b2170 ("net: fix sock_wake_async() rcu protection") > > Commit ceb5d58b2170 ("net: fix sock_wake_async() rcu protection") from > the current 4.4 release cycle introduces a new flags member in > struct socket_wq and moved SOCKWQ_ASYNC_NOSPACE and SOCKWQ_ASYNC_WAITDATA > from struct socket's flags member into that new place. > > Unfortunately, the new flags field is never initialized properly, at least > not for the struct socket_wq instance created in sock_alloc_inode(). > > One particular issue I encountered because of this is that my GNU Emacs > failed to draw anything on my desktop -- i.e. what I got is a transparent > window, including the title bar. Bisection lead to the commit mentioned > above and further investigation by means of strace told me that Emacs > is indeed speaking to my Xorg through an O_ASYNC AF_UNIX socket. This is > reproducible 100% of times and the fact that properly initializing the > struct socket_wq ->flags fixes the issue leads me to the conclusion that > somehow SOCKWQ_ASYNC_NOSPACE got set in the uninitialized ->flags, > preventing my Emacs from receiving any SIGIO's due to send space becoming > available again and it got stuck. > > Make sock_alloc_inode() set the newly created struct socket_wq's ->flags > member to zero. > > Signed-off-by: Nicolai Stange <nicstange@gmail.com> > --- > net/socket.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/socket.c b/net/socket.c > index 29822d6..d730ef9 100644 > --- a/net/socket.c > +++ b/net/socket.c > @@ -257,6 +257,7 @@ static struct inode *sock_alloc_inode(struct super_block *sb) > } > init_waitqueue_head(&wq->wait); > wq->fasync_list = NULL; > + wq->flags = 0; > RCU_INIT_POINTER(ei->socket.wq, wq); > > ei->socket.state = SS_UNCONNECTED;
Thanks a lot Nicolai for finding this. I completely overlooked this initial value.
I checked other places where 'struct socket_wq' were allocated and they look fine.
Acked-by: Eric Dumazet <edumazet@google.com>
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