netdev - [PATCH net-next 02/10] udp: move udp->no_check6_tx to udp->udp

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Date: Tue, 12 Sep 2023 09:17:22 +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: netdev@...r.kernel.org, Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>, 
	syzbot <syzkaller@...glegroups.com>
Subject: [PATCH net-next 02/10] udp: move udp->no_check6_tx to udp->udp_flags

syzbot reported that udp->no_check6_tx can be read locklessly.
Use one atomic bit from udp->udp_flags

Fixes: 1c19448c9ba6 ("net: Make enabling of zero UDP6 csums more restrictive")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/linux/udp.h | 10 +++++-----
 net/ipv4/udp.c      |  4 ++--
 net/ipv6/udp.c      |  4 ++--
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/linux/udp.h b/include/linux/udp.h
index 23f0693e0d9cc4212ab7c7dc982561a2807b14f0..e3f2a6c7ac1d1bb37720420ce4cb0dc223926866 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -34,6 +34,7 @@ static inline u32 udp_hashfn(const struct net *net, u32 num, u32 mask)
 
 enum {
 	UDP_FLAGS_CORK,		/* Cork is required */
+	UDP_FLAGS_NO_CHECK6_TX, /* Send zero UDP6 checksums on TX? */
 };
 
 struct udp_sock {
@@ -47,8 +48,7 @@ struct udp_sock {
 
 	int		 pending;	/* Any pending frames ? */
 	__u8		 encap_type;	/* Is this an Encapsulation socket? */
-	unsigned char	 no_check6_tx:1,/* Send zero UDP6 checksums on TX? */
-			 no_check6_rx:1,/* Allow zero UDP6 checksums on RX? */
+	unsigned char	 no_check6_rx:1,/* Allow zero UDP6 checksums on RX? */
 			 encap_enabled:1, /* This socket enabled encap
 					   * processing; UDP tunnels and
 					   * different encapsulation layer set
@@ -115,7 +115,7 @@ struct udp_sock {
 
 static inline void udp_set_no_check6_tx(struct sock *sk, bool val)
 {
-	udp_sk(sk)->no_check6_tx = val;
+	udp_assign_bit(NO_CHECK6_TX, sk, val);
 }
 
 static inline void udp_set_no_check6_rx(struct sock *sk, bool val)
@@ -123,9 +123,9 @@ static inline void udp_set_no_check6_rx(struct sock *sk, bool val)
 	udp_sk(sk)->no_check6_rx = val;
 }
 
-static inline bool udp_get_no_check6_tx(struct sock *sk)
+static inline bool udp_get_no_check6_tx(const struct sock *sk)
 {
-	return udp_sk(sk)->no_check6_tx;
+	return udp_test_bit(NO_CHECK6_TX, sk);
 }
 
 static inline bool udp_get_no_check6_rx(struct sock *sk)
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 9709f8a532dc3d0e62a1cdb126ea7dc3cebd7da9..0c6998291c99d70d7d1f7e98af241642f75c1c22 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2694,7 +2694,7 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case UDP_NO_CHECK6_TX:
-		up->no_check6_tx = valbool;
+		udp_set_no_check6_tx(sk, valbool);
 		break;
 
 	case UDP_NO_CHECK6_RX:
@@ -2791,7 +2791,7 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case UDP_NO_CHECK6_TX:
-		val = up->no_check6_tx;
+		val = udp_get_no_check6_tx(sk);
 		break;
 
 	case UDP_NO_CHECK6_RX:
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 0c6973cd22ce4cdcc846eb94029f4281e900da40..469df0ca561f762f31deea1ca1836d49be7a9f3c 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1241,7 +1241,7 @@ static int udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6,
 			kfree_skb(skb);
 			return -EINVAL;
 		}
-		if (udp_sk(sk)->no_check6_tx) {
+		if (udp_get_no_check6_tx(sk)) {
 			kfree_skb(skb);
 			return -EINVAL;
 		}
@@ -1262,7 +1262,7 @@ static int udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6,
 
 	if (is_udplite)
 		csum = udplite_csum(skb);
-	else if (udp_sk(sk)->no_check6_tx) {   /* UDP csum disabled */
+	else if (udp_get_no_check6_tx(sk)) {   /* UDP csum disabled */
 		skb->ip_summed = CHECKSUM_NONE;
 		goto send;
 	} else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */
-- 
2.42.0.283.g2d96d420d3-goog