Patch "inet: fix potential deadlock in reqsk_queue_unlink()" has been added to the 4.1-stable tree

Patch "inet: fix potential deadlock in reqsk_queue_unlink()" has been added to the 4.1-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    inet: fix potential deadlock in reqsk_queue_unlink()

to the 4.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     inet-fix-potential-deadlock-in-reqsk_queue_unlink.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 83fccfc3940c4a2db90fd7e7079f5b465cd8c6af Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Thu, 13 Aug 2015 15:44:51 -0700
Subject: inet: fix potential deadlock in reqsk_queue_unlink()

From: Eric Dumazet <edumazet@google.com>

commit 83fccfc3940c4a2db90fd7e7079f5b465cd8c6af upstream.

When replacing del_timer() with del_timer_sync(), I introduced
a deadlock condition :

reqsk_queue_unlink() is called from inet_csk_reqsk_queue_drop()

inet_csk_reqsk_queue_drop() can be called from many contexts,
one being the timer handler itself (reqsk_timer_handler()).

In this case, del_timer_sync() loops forever.

Simple fix is to test if timer is pending.

Fixes: 2235f2ac75fd ("inet: fix races with reqsk timers")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Holger Hoffstätte <holger.hoffstaette@googlemail.com>
Cc: Andre Tomt <andre@tomt.net>
Cc: Chris Caputo <ccaputo@alt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/ipv4/inet_connection_sock.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -584,7 +584,7 @@ static bool reqsk_queue_unlink(struct re
 	}
 
 	spin_unlock(&queue->syn_wait_lock);
-	if (del_timer_sync(&req->rsk_timer))
+	if (timer_pending(&req->rsk_timer) && del_timer_sync(&req->rsk_timer))
 		reqsk_put(req);
 	return found;
 }


Patches currently in stable-queue which might be from edumazet@google.com are

queue-4.1/inet-fix-potential-deadlock-in-reqsk_queue_unlink.patch