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Patch "netlink: Call cb->done from a worker thread" has been added to the 4.8-stable tree

PATCH [email protected] 1 participant 1 message Dec 8, 2016

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

    netlink: Call cb->done from a worker thread

to the 4.8-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:
netlink-call-cb-done-from-a-worker-thread.patch
and it can be found in the queue-4.8 subdirectory.

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

Quoted 1 line

From foo@baz Thu Dec 8 07:19:12 CET 2016

From: Herbert Xu <[email protected]>
Date: Mon, 28 Nov 2016 19:22:12 +0800
Subject: netlink: Call cb->done from a worker thread

From: Herbert Xu <[email protected]>

[ Upstream commit 707693c8a498697aa8db240b93eb76ec62e30892 ]

The cb->done interface expects to be called in process context. This was broken by the netlink RCU conversion. This patch fixes it by adding a worker struct to make the cb->done call where necessary.

Fixes 21e4902aea80 ("netlink: Lockless lookup with RCU grace...")
Reported-by Subash Abhinov Kasiviswanathan <[email protected]>
Signed-off-by Herbert Xu <[email protected]>
Acked-by Cong Wang <[email protected]>
Signed-off-by David S. Miller <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 net/netlink/af_netlink.c |   27 +++++++++++++++++++++++----
 net/netlink/af_netlink.h |    2 ++
 2 files changed, 25 insertions(+), 4 deletions(-)
net/netlink/af_netlink.c +23 -4
@@ -322,14 +322,11 @@ static void netlink_skb_set_owner_r(stru
 	sk_mem_charge(sk, skb->truesize);
 }
 
-static void netlink_sock_destruct(struct sock *sk)
+static void __netlink_sock_destruct(struct sock *sk)
 {
 	struct netlink_sock *nlk = nlk_sk(sk);
 
 	if (nlk->cb_running) {
-		if (nlk->cb.done)
-			nlk->cb.done(&nlk->cb);
-
 		module_put(nlk->cb.module);
 		kfree_skb(nlk->cb.skb);
 	}

@@ -346,6 +343,28 @@ static void netlink_sock_destruct(struct
 	WARN_ON(nlk_sk(sk)->groups);
 }
 
+static void netlink_sock_destruct_work(struct work_struct *work)
+{
+	struct netlink_sock *nlk = container_of(work, struct netlink_sock,
+						work);
+
+	nlk->cb.done(&nlk->cb);
+	__netlink_sock_destruct(&nlk->sk);
+}
+
+static void netlink_sock_destruct(struct sock *sk)
+{
+	struct netlink_sock *nlk = nlk_sk(sk);
+
+	if (nlk->cb_running && nlk->cb.done) {
+		INIT_WORK(&nlk->work, netlink_sock_destruct_work);
+		schedule_work(&nlk->work);
+		return;
+	}
+
+	__netlink_sock_destruct(sk);
+}
+
 /* This lock without WQ_FLAG_EXCLUSIVE is good on UP and it is _very_ bad on
  * SMP. Look, when several writers sleep and reader wakes them up, all but one
  * immediately hit write lock and grab all the cpus. Exclusive sleep solves
net/netlink/af_netlink.h +2 -0
@@ -3,6 +3,7 @@
 
 #include <linux/rhashtable.h>
 #include <linux/atomic.h>
+#include <linux/workqueue.h>
 #include <net/sock.h>
 
 #define NLGRPSZ(x)	(ALIGN(x, sizeof(unsigned long) * 8) / 8)

@@ -33,6 +34,7 @@ struct netlink_sock {
 
 	struct rhash_head	node;
 	struct rcu_head		rcu;
+	struct work_struct	work;
 };
 
 static inline struct netlink_sock *nlk_sk(struct sock *sk)

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

queue-4.8/udplite-call-proper-backlog-handlers.patch queue-4.8/netlink-do-not-schedule-work-from-sk_destruct.patch queue-4.8/netlink-call-cb-done-from-a-worker-thread.patch