From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Wed, 19 Apr 2017 13:17:55 +0000 (+0200)
Subject: 3.18 patch
X-Git-Tag: v4.4.63~7
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d5c35481ad9a7869854af97d2aebd183a70c7d30;p=thirdparty%2Fkernel%2Fstable-queue.git

3.18 patch
---

diff --git a/queue-3.18/sctp-deny-peeloff-operation-on-asocs-with-threads-sleeping-on-it.patch b/queue-3.18/sctp-deny-peeloff-operation-on-asocs-with-threads-sleeping-on-it.patch
new file mode 100644
index 00000000000..f8df6c0ae05
--- /dev/null
+++ b/queue-3.18/sctp-deny-peeloff-operation-on-asocs-with-threads-sleeping-on-it.patch
@@ -0,0 +1,66 @@
+From dfcb9f4f99f1e9a49e43398a7bfbf56927544af1 Mon Sep 17 00:00:00 2001
+From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
+Date: Thu, 23 Feb 2017 09:31:18 -0300
+Subject: sctp: deny peeloff operation on asocs with threads sleeping on it
+
+From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
+
+commit dfcb9f4f99f1e9a49e43398a7bfbf56927544af1 upstream.
+
+commit 2dcab5984841 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
+attempted to avoid a BUG_ON call when the association being used for a
+sendmsg() is blocked waiting for more sndbuf and another thread did a
+peeloff operation on such asoc, moving it to another socket.
+
+As Ben Hutchings noticed, then in such case it would return without
+locking back the socket and would cause two unlocks in a row.
+
+Further analysis also revealed that it could allow a double free if the
+application managed to peeloff the asoc that is created during the
+sendmsg call, because then sctp_sendmsg() would try to free the asoc
+that was created only for that call.
+
+This patch takes another approach. It will deny the peeloff operation
+if there is a thread sleeping on the asoc, so this situation doesn't
+exist anymore. This avoids the issues described above and also honors
+the syscalls that are already being handled (it can be multiple sendmsg
+calls).
+
+Joint work with Xin Long.
+
+Fixes: 2dcab5984841 ("sctp: avoid BUG_ON on sctp_wait_for_sndbuf")
+Cc: Alexander Popov <alex.popov@linux.com>
+Cc: Ben Hutchings <ben@decadent.org.uk>
+Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
+Signed-off-by: Xin Long <lucien.xin@gmail.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ net/sctp/socket.c |    8 ++++++--
+ 1 file changed, 6 insertions(+), 2 deletions(-)
+
+--- a/net/sctp/socket.c
++++ b/net/sctp/socket.c
+@@ -4433,6 +4433,12 @@ int sctp_do_peeloff(struct sock *sk, sct
+ 	if (!asoc)
+ 		return -EINVAL;
+ 
++	/* If there is a thread waiting on more sndbuf space for
++	 * sending on this asoc, it cannot be peeled.
++	 */
++	if (waitqueue_active(&asoc->wait))
++		return -EBUSY;
++
+ 	/* An association cannot be branched off from an already peeled-off
+ 	 * socket, nor is this supported for tcp style sockets.
+ 	 */
+@@ -6965,8 +6971,6 @@ static int sctp_wait_for_sndbuf(struct s
+ 		 */
+ 		release_sock(sk);
+ 		current_timeo = schedule_timeout(current_timeo);
+-		if (sk != asoc->base.sk)
+-			goto do_error;
+ 		lock_sock(sk);
+ 
+ 		*timeo_p = current_timeo;
diff --git a/queue-3.18/series b/queue-3.18/series
index d1703d83b0e..56a9e951bfd 100644
--- a/queue-3.18/series
+++ b/queue-3.18/series
@@ -62,3 +62,4 @@ rtl8150-use-heap-buffers-for-all-register-access.patch
 catc-combine-failure-cleanup-code-in-catc_probe.patch
 catc-use-heap-buffer-for-memory-size-test.patch
 net-ipv6-check-route-protocol-when-deleting-routes.patch
+sctp-deny-peeloff-operation-on-asocs-with-threads-sleeping-on-it.patch