udp: annotate data-races around udp->encap_type
[ Upstream commit 70a36f571362a8de8b8c02d21ae524fc776287f2 ]
syzbot/KCSAN complained about UDP_ENCAP_L2TPINUDP setsockopt() racing.
Add READ_ONCE()/WRITE_ONCE() to document races on this lockless field.
syzbot report was:
BUG: KCSAN: data-race in udp_lib_setsockopt / udp_lib_setsockopt
read-write to 0xffff8881083603fa of 1 bytes by task 16557 on cpu 0:
udp_lib_setsockopt+0x682/0x6c0
udp_setsockopt+0x73/0xa0 net/ipv4/udp.c:2779
sock_common_setsockopt+0x61/0x70 net/core/sock.c:3697
__sys_setsockopt+0x1c9/0x230 net/socket.c:2263
__do_sys_setsockopt net/socket.c:2274 [inline]
__se_sys_setsockopt net/socket.c:2271 [inline]
__x64_sys_setsockopt+0x66/0x80 net/socket.c:2271
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
read-write to 0xffff8881083603fa of 1 bytes by task 16554 on cpu 1:
udp_lib_setsockopt+0x682/0x6c0
udp_setsockopt+0x73/0xa0 net/ipv4/udp.c:2779
sock_common_setsockopt+0x61/0x70 net/core/sock.c:3697
__sys_setsockopt+0x1c9/0x230 net/socket.c:2263
__do_sys_setsockopt net/socket.c:2274 [inline]
__se_sys_setsockopt net/socket.c:2271 [inline]
__x64_sys_setsockopt+0x66/0x80 net/socket.c:2271
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x01 -> 0x05
Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16554 Comm: syz-executor.5 Not tainted 6.5.0-rc7-syzkaller-00004-gf7757129e3de #0
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot <[email protected]>
Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Willem de Bruijn <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 90688877..0e79d18 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -571,7 +571,7 @@ int __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
sk = __udp6_lib_lookup(net, daddr, uh->dest, saddr, uh->source,
inet6_iif(skb), inet6_sdif(skb), udptable, NULL);
- if (!sk || udp_sk(sk)->encap_type) {
+ if (!sk || READ_ONCE(udp_sk(sk)->encap_type)) {
/* No socket for error: try tunnels before discarding */
if (static_branch_unlikely(&udpv6_encap_needed_key)) {
sk = __udp6_lib_err_encap(net, hdr, offset, uh,
@@ -688,7 +688,8 @@ static int udpv6_queue_rcv_one_skb(struct sock *sk, struct sk_buff *skb)
}
nf_reset_ct(skb);
- if (static_branch_unlikely(&udpv6_encap_needed_key) && up->encap_type) {
+ if (static_branch_unlikely(&udpv6_encap_needed_key) &&
+ READ_ONCE(up->encap_type)) {
int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
/*
diff --git a/net/ipv6/xfrm6_input.c b/net/ipv6/xfrm6_input.c
index 4907ab2..4156387 100644
--- a/net/ipv6/xfrm6_input.c
+++ b/net/ipv6/xfrm6_input.c
@@ -81,14 +81,14 @@ int xfrm6_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
struct ipv6hdr *ip6h;
int len;
int ip6hlen = sizeof(struct ipv6hdr);
-
__u8 *udpdata;
__be32 *udpdata32;
- __u16 encap_type = up->encap_type;
+ u16 encap_type;
if (skb->protocol == htons(ETH_P_IP))
return xfrm4_udp_encap_rcv(sk, skb);
+ encap_type = READ_ONCE(up->encap_type);
/* if this is not encapsulated socket, then just return now */
if (!encap_type)
return 1;
