[PATCH 3.2 68/77] sctp: update the netstamp_needed counter when copying sockets

[Ben Hutchings]

3.2.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>

[ Upstream commit 01ce63c90170283a9855d1db4fe81934dddce648 ]

Dmitry Vyukov reported that SCTP was triggering a WARN on socket destroy
related to disabling sock timestamp.

When SCTP accepts an association or peel one off, it copies sock flags
but forgot to call net_enable_timestamp() if a packet timestamping flag
was copied, leading to extra calls to net_disable_timestamp() whenever
such clones were closed.

The fix is to call net_enable_timestamp() whenever we copy a sock with
that flag on, like tcp does.

Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Acked-by: Vlad Yasevich <vyasevich@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.2: SK_FLAGS_TIMESTAMP is newly defined]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -565,6 +565,8 @@ enum sock_flags {
 	SOCK_ZEROCOPY, /* buffers from userspace */
 };
 
+#define SK_FLAGS_TIMESTAMP ((1UL << SOCK_TIMESTAMP) | (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE))
+
 static inline void sock_copy_flags(struct sock *nsk, struct sock *osk)
 {
 	nsk->sk_flags = osk->sk_flags;
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -6731,6 +6731,9 @@ void sctp_copy_sock(struct sock *newsk,
 	newinet->mc_ttl = 1;
 	newinet->mc_index = 0;
 	newinet->mc_list = NULL;
+
+	if (newsk->sk_flags & SK_FLAGS_TIMESTAMP)
+		net_enable_timestamp();
 }
 
 static inline void sctp_copy_descendant(struct sock *sk_to,

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