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udp: annotate data-races around udp->encap_type

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[ Upstream commit 70a36f5713 ]

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: 1da177e4c3 ("Linux-2.6.12-rc2")
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eric Dumazet
2023-09-12 09:17:28 +00:00
committed by Greg Kroah-Hartman
parent f1f1f5cc19
commit 4781a75d34
6 changed files with 17 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
net/ipv4/udp.c
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@@ -714,7 +714,7 @@ int __udp4_lib_err(struct sk_buff *skb, u32 info, struct udp_table *udptable)
iph->saddr, uh->source, skb->dev->ifindex,
inet_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(&udp_encap_needed_key)) {
sk = __udp4_lib_err_encap(net, iph, uh, udptable, sk, skb,
@@ -2081,7 +2081,8 @@ static int udp_queue_rcv_one_skb(struct sock *sk, struct sk_buff *skb)
}
nf_reset_ct(skb);
if (static_branch_unlikely(&udp_encap_needed_key) && up->encap_type) {
if (static_branch_unlikely(&udp_encap_needed_key) &&
READ_ONCE(up->encap_type)) {
int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
/*
@@ -2684,7 +2685,7 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
#endif
fallthrough;
case UDP_ENCAP_L2TPINUDP:
up->encap_type = val;
WRITE_ONCE(up->encap_type, val);
udp_tunnel_encap_enable(sk);
break;
default:
@@ -2785,7 +2786,7 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
break;
case UDP_ENCAP:
val = up->encap_type;
val = READ_ONCE(up->encap_type);
break;
case UDP_NO_CHECK6_TX: