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List:       git-commits-head
Subject:    net, socket, socket_wq: fix missing initialization of flags
From:       "Linux Kernel Mailing List" <linux-kernel () vger ! kernel ! org>
Date:       2015-12-31 22:51:34
Message-ID: 20151231225134.750576612A2 () gitolite ! kernel ! org
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Web:        https://git.kernel.org/torvalds/c/574aab1e02837927e3c94193eedf94128ad10b6d
Commit:     574aab1e02837927e3c94193eedf94128ad10b6d
Parent:     c1e3334fa4b2891752f1367b47a60209353ba2f5
Refname:    refs/heads/master
Author:     Nicolai Stange <nicstange@gmail.com>
AuthorDate: Tue Dec 29 13:29:55 2015 +0100
Committer:  David S. Miller <davem@davemloft.net>
CommitDate: Wed Dec 30 16:38:01 2015 -0500

    net, socket, socket_wq: fix missing initialization of flags
    
    Commit ceb5d58b2170 ("net: fix sock_wake_async() rcu protection") from
    the current 4.4 release cycle introduced 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_WAITDATA got set in the uninitialized ->flags,
    preventing my Emacs from receiving any SIGIO's due to data becoming
    available and it got stuck.
    
    Make sock_alloc_inode() set the newly created struct socket_wq's ->flags
    member to zero.
    
    Fixes: ceb5d58b2170 ("net: fix sock_wake_async() rcu protection")
    Signed-off-by: Nicolai Stange <nicstange@gmail.com>
    Acked-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
---
 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;
--
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