netdev - [PATCH v2 net-next 04/15] ipv6: annotate data-races around cnf.mtu6

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Date: Tue, 27 Feb 2024 15:01:49 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, Jiri Pirko <jiri@...dia.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 net-next 04/15] ipv6: annotate data-races around cnf.mtu6

idev->cnf.mtu6 might be read locklessly, add appropriate READ_ONCE()
and WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/ip6_route.h | 2 +-
 net/ipv6/addrconf.c     | 4 ++--
 net/ipv6/ndisc.c        | 4 ++--
 net/ipv6/route.c        | 6 +++---
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 52a51c69aa9de2fe1e6d351997f5b3d94862521a..a30c6aa9e5cf3e442cd29e2d169ba0b0d46a1f46 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -332,7 +332,7 @@ static inline unsigned int ip6_dst_mtu_maybe_forward(const struct dst_entry *dst
 	rcu_read_lock();
 	idev = __in6_dev_get(dst->dev);
 	if (idev)
-		mtu = idev->cnf.mtu6;
+		mtu = READ_ONCE(idev->cnf.mtu6);
 	rcu_read_unlock();
 
 out:
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 88b129b7884564876a51b359137c33e9b75ee9de..92ae6d62e4917749c5788aefda6752466061e6f8 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3671,7 +3671,7 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
 
 		if (idev) {
 			rt6_mtu_change(dev, dev->mtu);
-			idev->cnf.mtu6 = dev->mtu;
+			WRITE_ONCE(idev->cnf.mtu6, dev->mtu);
 			break;
 		}
 
@@ -3763,7 +3763,7 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
 			if (idev->cnf.mtu6 != dev->mtu &&
 			    dev->mtu >= IPV6_MIN_MTU) {
 				rt6_mtu_change(dev, dev->mtu);
-				idev->cnf.mtu6 = dev->mtu;
+				WRITE_ONCE(idev->cnf.mtu6, dev->mtu);
 			}
 			WRITE_ONCE(idev->tstamp, jiffies);
 			inet6_ifinfo_notify(RTM_NEWLINK, idev);
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 8523f0595b01899a9f6cf82809c1b4bcfc233202..e96d79cd34d27ca304c5f71b6db41b99d2dd8856 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1578,8 +1578,8 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 
 		if (mtu < IPV6_MIN_MTU || mtu > skb->dev->mtu) {
 			ND_PRINTK(2, warn, "RA: invalid mtu: %d\n", mtu);
-		} else if (in6_dev->cnf.mtu6 != mtu) {
-			in6_dev->cnf.mtu6 = mtu;
+		} else if (READ_ONCE(in6_dev->cnf.mtu6) != mtu) {
+			WRITE_ONCE(in6_dev->cnf.mtu6, mtu);
 			fib6_metric_set(rt, RTAX_MTU, mtu);
 			rt6_mtu_change(skb->dev, mtu);
 		}
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 707d65bc9c0e5e9b2900063f0ac86c3c5e299088..66c685b0b6199fee3bc39768eab5a6fb831bd2f5 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1596,7 +1596,7 @@ static unsigned int fib6_mtu(const struct fib6_result *res)
 
 		rcu_read_lock();
 		idev = __in6_dev_get(dev);
-		mtu = idev->cnf.mtu6;
+		mtu = READ_ONCE(idev->cnf.mtu6);
 		rcu_read_unlock();
 	}
 
@@ -3249,8 +3249,8 @@ u32 ip6_mtu_from_fib6(const struct fib6_result *res,
 
 		mtu = IPV6_MIN_MTU;
 		idev = __in6_dev_get(dev);
-		if (idev && idev->cnf.mtu6 > mtu)
-			mtu = idev->cnf.mtu6;
+		if (idev)
+			mtu = max_t(u32, mtu, READ_ONCE(idev->cnf.mtu6));
 	}
 
 	mtu = min_t(unsigned int, mtu, IP6_MAX_MTU);
-- 
2.44.0.rc1.240.g4c46232300-goog