Patch "netlink: Do not schedule work from sk_destruct" has been added to the 4.8-stable tree

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

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2016-12-08 06:22 UTC #0 lore raw

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

netlink: Do not schedule work from sk_destruct

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-do-not-schedule-work-from-sk_destruct.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, 5 Dec 2016 15:28:21 +0800
Subject: netlink: Do not schedule work from sk_destruct

From: Herbert Xu <[email protected]>

[ Upstream commit ed5d7788a934a4b6d6d025e948ed4da496b4f12e ]

It is wrong to schedule a work from sk_destruct using the socket as the memory reserve because the socket will be freed immediately after the return from sk_destruct.

Instead we should do the deferral prior to sk_free.

This patch does just that.

Fixes 707693c8a498 ("netlink: Call cb->done from a worker thread")

Signed-off-by Herbert Xu <[email protected]>

Tested-by Andrey Konovalov <[email protected]>

Signed-off-by David S. Miller <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 net/netlink/af_netlink.c |   32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

net/netlink/af_netlink.c +15 ~~-17~~

@@ -322,11 +322,13 @@ 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);
 	}

@@ -348,21 +350,7 @@ static void netlink_sock_destruct_work(s
 	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);
+	sk_free(&nlk->sk);
 }
 
 /* This lock without WQ_FLAG_EXCLUSIVE is good on UP and it is _very_ bad on

@@ -667,8 +655,18 @@ out_module:
 static void deferred_put_nlk_sk(struct rcu_head *head)
 {
 	struct netlink_sock *nlk = container_of(head, struct netlink_sock, rcu);
+	struct sock *sk = &nlk->sk;
+
+	if (!atomic_dec_and_test(&sk->sk_refcnt))
+		return;
+
+	if (nlk->cb_running && nlk->cb.done) {
+		INIT_WORK(&nlk->work, netlink_sock_destruct_work);
+		schedule_work(&nlk->work);
+		return;
+	}
 
-	sock_put(&nlk->sk);
+	sk_free(sk);
 }
 
 static int netlink_release(struct socket *sock)

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