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@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/include/linux/udp.h b/include/linux/udp.h
index 23f0693e0d9cc4212ab7c7dc982561a2807b14f0..e3f2a6c7ac1d1bb37720420ce4cb0dc223926866 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 */