Patch "tipc: make macro tipc_wait_for_cond() smp safe" has been added to the 4.11-stable tree

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

tipc: make macro tipc_wait_for_cond() smp safe

to the 4.11-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:
tipc-make-macro-tipc_wait_for_cond-smp-safe.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jon Paul Maloy <[email protected]>
Date: Thu, 11 May 2017 20:28:15 +0200
Subject: tipc: make macro tipc_wait_for_cond() smp safe

From: Jon Paul Maloy <[email protected]>

[ Upstream commit 844cf763fba654436d3a4279b6a672c196cf1901 ]

The macro tipc_wait_for_cond() is embedding the macro sk_wait_event() to fulfil its task. The latter, in turn, is evaluating the stated condition outside the socket lock context. This is problematic if the condition is accessing non-trivial data structures which may be altered by incoming interrupts, as is the case with the cong_links() linked list, used by socket to keep track of the current set of congested links. We sometimes see crashes when this list is accessed by a condition function at the same time as a SOCK_WAKEUP interrupt is removing an element from the list.

We fix this by expanding selected parts of sk_wait_event() into the outer macro, while ensuring that all evaluations of a given condition are performed under socket lock protection.

---
 net/tipc/socket.c |   38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

@@ -361,25 +361,25 @@ static int tipc_sk_sock_err(struct socke
 	return 0;
 }
 
-#define tipc_wait_for_cond(sock_, timeout_, condition_)			\
-({								        \
-	int rc_ = 0;							\
-	int done_ = 0;							\
-									\
-	while (!(condition_) && !done_) {				\
-		struct sock *sk_ = sock->sk;				\
-		DEFINE_WAIT_FUNC(wait_, woken_wake_function);		\
-									\
-		rc_ = tipc_sk_sock_err(sock_, timeout_);		\
-		if (rc_)						\
-			break;						\
-		prepare_to_wait(sk_sleep(sk_), &wait_,			\
-				TASK_INTERRUPTIBLE);			\
-		done_ = sk_wait_event(sk_, timeout_,			\
-				      (condition_), &wait_);		\
-		remove_wait_queue(sk_sleep(sk_), &wait_);		\
-	}								\
-	rc_;								\
+#define tipc_wait_for_cond(sock_, timeo_, condition_)			       \
+({                                                                             \
+	struct sock *sk_;						       \
+	int rc_;							       \
+									       \
+	while ((rc_ = !(condition_))) {					       \
+		DEFINE_WAIT_FUNC(wait_, woken_wake_function);	               \
+		sk_ = (sock_)->sk;					       \
+		rc_ = tipc_sk_sock_err((sock_), timeo_);		       \
+		if (rc_)						       \
+			break;						       \
+		prepare_to_wait(sk_sleep(sk_), &wait_, TASK_INTERRUPTIBLE);    \
+		release_sock(sk_);					       \
+		*(timeo_) = wait_woken(&wait_, TASK_INTERRUPTIBLE, *(timeo_)); \
+		sched_annotate_sleep();				               \
+		lock_sock(sk_);						       \
+		remove_wait_queue(sk_sleep(sk_), &wait_);		       \
+	}								       \
+	rc_;								       \
 })
 
 /**

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/tipc-make-macro-tipc_wait_for_cond-smp-safe.patch