| Message ID | 87ege73bma.fsf@gmail.com |
|---|---|
| State | Superseded, archived |
| Delegated to: | David Miller |
| Headers | show |
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> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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;
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(+)