From 70a36f571362a8de8b8c02d21ae524fc776287f2 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 12 Sep 2023 09:17:28 +0000 Subject: udp: annotate data-races around udp->encap_type 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 Signed-off-by: Eric Dumazet Reviewed-by: Willem de Bruijn Signed-off-by: Paolo Abeni --- net/ipv4/xfrm4_input.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/ipv4/xfrm4_input.c') diff --git a/net/ipv4/xfrm4_input.c b/net/ipv4/xfrm4_input.c index eac206a290d0..183f6dc37242 100644 --- a/net/ipv4/xfrm4_input.c +++ b/net/ipv4/xfrm4_input.c @@ -85,11 +85,11 @@ int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb) struct udphdr *uh; struct iphdr *iph; int iphlen, len; - __u8 *udpdata; __be32 *udpdata32; - __u16 encap_type = up->encap_type; + u16 encap_type; + encap_type = READ_ONCE(up->encap_type); /* if this is not encapsulated socket, then just return now */ if (!encap_type) return 1; -- cgit v1.2.3