[PATCH 4.19 051/120] udp: annotate data races around unix_sk(sk)->gso_size

Greg Kroah-Hartman
2021-07-26T16:01:19Z

From: Eric Dumazet <edumazet@google.com>

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: bec1f6f69736 ("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>
---
net/ipv4/udp.c | 6 +++---
net/ipv6/udp.c | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)

--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -997,7 +997,7 @@ int udp_sendmsg(struct sock *sk, struct
}

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,
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,
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
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1175,7 +1175,7 @@ int udpv6_sendmsg(struct sock *sk, struc
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 */