Commit dd1f607c authored Jun 30, 2021 by Eric Dumazet Committed by Greg Kroah-Hartman Jul 28, 2021

udp: annotate data races around unix_sk(sk)->gso_size



commit 18a419bad63b7f68a1979e28459782518e7b6bbe upstream.

Accesses to unix_sk(sk)->gso_size are lockless.
Add READ_ONCE()/WRITE_ONCE() around them.

BUG: KCSAN: data-race in udp_lib_setsockopt / udpv6_sendmsg

write to 0xffff88812d78f47c of 2 bytes by task 10849 on cpu 1:
 udp_lib_setsockopt+0x3b3/0x710 net/ipv4/udp.c:2696
 udpv6_setsockopt+0x63/0x90 net/ipv6/udp.c:1630
 sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3265
 __sys_setsockopt+0x18f/0x200 net/socket.c:2104
 __do_sys_setsockopt net/socket.c:2115 [inline]
 __se_sys_setsockopt net/socket.c:2112 [inline]
 __x64_sys_setsockopt+0x62/0x70 net/socket.c:2112
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812d78f47c of 2 bytes by task 10852 on cpu 0:
 udpv6_sendmsg+0x161/0x16b0 net/ipv6/udp.c:1299
 inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:642
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg net/socket.c:674 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2337
 ___sys_sendmsg net/socket.c:2391 [inline]
 __sys_sendmmsg+0x315/0x4b0 net/socket.c:2477
 __do_sys_sendmmsg net/socket.c:2506 [inline]
 __se_sys_sendmmsg net/socket.c:2503 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2503
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000 -> 0x0005

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10852 Comm: syz-executor.0 Not tainted 5.13.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Fixes: bec1f6f6 ("udp: generate gso with UDP_SEGMENT")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 4416df72

net/ipv4/udp.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -997,7 +997,7 @@ int udp_sendmsg(struct sock sk, struct msghdr msg, size_t len)
		}

		ipcm_init_sk(&ipc, inet);
		ipc.gso_size = up->gso_size;
		ipc.gso_size = READ_ONCE(up->gso_size);

		if (msg->msg_controllen) {
		err = udp_cmsg_send(sk, msg, &ipc.gso_size);
		@@ -2505,7 +2505,7 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
		case UDP_SEGMENT:
		if (val < 0 \|\| val > USHRT_MAX)
		return -EINVAL;
		up->gso_size = val;
		WRITE_ONCE(up->gso_size, val);
		break;

		/*
		@@ -2599,7 +2599,7 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
		break;

		case UDP_SEGMENT:
		val = up->gso_size;
		val = READ_ONCE(up->gso_size);
		break;

		/* The following two cannot be changed on UDP sockets, the return is

net/ipv6/udp.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1175,7 +1175,7 @@ int udpv6_sendmsg(struct sock sk, struct msghdr msg, size_t len)
		int (getfrag)(void , char , int, int, int, struct sk_buff );

		ipcm6_init(&ipc6);
		ipc6.gso_size = up->gso_size;
		ipc6.gso_size = READ_ONCE(up->gso_size);
		ipc6.sockc.tsflags = sk->sk_tsflags;

		/* destination address check */