[PATCH 4.19 022/245] net: silence data-races on sk_backlog.tail

From: Greg Kroah-Hartman
Date: Tue Sep 29 2020 - 08:32:04 EST

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From: Eric Dumazet <edumazet@xxxxxxxxxx>

[ Upstream commit 9ed498c6280a2f2b51d02df96df53037272ede49 ]

sk->sk_backlog.tail might be read without holding the socket spinlock,
we need to add proper READ_ONCE()/WRITE_ONCE() to silence the warnings.

KCSAN reported :

BUG: KCSAN: data-race in tcp_add_backlog / tcp_recvmsg

write to 0xffff8881265109f8 of 8 bytes by interrupt on cpu 1:
__sk_add_backlog include/net/sock.h:907 [inline]
sk_add_backlog include/net/sock.h:938 [inline]
tcp_add_backlog+0x476/0xce0 net/ipv4/tcp_ipv4.c:1759
tcp_v4_rcv+0x1a70/0x1bd0 net/ipv4/tcp_ipv4.c:1947
ip_protocol_deliver_rcu+0x4d/0x420 net/ipv4/ip_input.c:204
ip_local_deliver_finish+0x110/0x140 net/ipv4/ip_input.c:231
NF_HOOK include/linux/netfilter.h:305 [inline]
NF_HOOK include/linux/netfilter.h:299 [inline]
ip_local_deliver+0x133/0x210 net/ipv4/ip_input.c:252
dst_input include/net/dst.h:442 [inline]
ip_rcv_finish+0x121/0x160 net/ipv4/ip_input.c:413
NF_HOOK include/linux/netfilter.h:305 [inline]
NF_HOOK include/linux/netfilter.h:299 [inline]
ip_rcv+0x18f/0x1a0 net/ipv4/ip_input.c:523
__netif_receive_skb_one_core+0xa7/0xe0 net/core/dev.c:4929
__netif_receive_skb+0x37/0xf0 net/core/dev.c:5043
netif_receive_skb_internal+0x59/0x190 net/core/dev.c:5133
napi_skb_finish net/core/dev.c:5596 [inline]
napi_gro_receive+0x28f/0x330 net/core/dev.c:5629
receive_buf+0x284/0x30b0 drivers/net/virtio_net.c:1061
virtnet_receive drivers/net/virtio_net.c:1323 [inline]
virtnet_poll+0x436/0x7d0 drivers/net/virtio_net.c:1428
napi_poll net/core/dev.c:6311 [inline]
net_rx_action+0x3ae/0xa90 net/core/dev.c:6379
__do_softirq+0x115/0x33f kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0xbb/0xe0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
do_IRQ+0xa6/0x180 arch/x86/kernel/irq.c:263
ret_from_intr+0x0/0x19
native_safe_halt+0xe/0x10 arch/x86/kernel/paravirt.c:71
arch_cpu_idle+0x1f/0x30 arch/x86/kernel/process.c:571
default_idle_call+0x1e/0x40 kernel/sched/idle.c:94
cpuidle_idle_call kernel/sched/idle.c:154 [inline]
do_idle+0x1af/0x280 kernel/sched/idle.c:263
cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:355
start_secondary+0x208/0x260 arch/x86/kernel/smpboot.c:264
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241

read to 0xffff8881265109f8 of 8 bytes by task 8057 on cpu 0:
tcp_recvmsg+0x46e/0x1b40 net/ipv4/tcp.c:2050
inet_recvmsg+0xbb/0x250 net/ipv4/af_inet.c:838
sock_recvmsg_nosec net/socket.c:871 [inline]
sock_recvmsg net/socket.c:889 [inline]
sock_recvmsg+0x92/0xb0 net/socket.c:885
sock_read_iter+0x15f/0x1e0 net/socket.c:967
call_read_iter include/linux/fs.h:1889 [inline]
new_sync_read+0x389/0x4f0 fs/read_write.c:414
__vfs_read+0xb1/0xc0 fs/read_write.c:427
vfs_read fs/read_write.c:461 [inline]
vfs_read+0x143/0x2c0 fs/read_write.c:446
ksys_read+0xd5/0x1b0 fs/read_write.c:587
__do_sys_read fs/read_write.c:597 [inline]
__se_sys_read fs/read_write.c:595 [inline]
__x64_sys_read+0x4c/0x60 fs/read_write.c:595
do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8057 Comm: syz-fuzzer Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/crypto/chelsio/chtls/chtls_io.c | 10 +++++-----
include/net/sock.h | 4 ++--
net/ipv4/tcp.c | 2 +-
net/llc/af_llc.c | 2 +-
4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/crypto/chelsio/chtls/chtls_io.c b/drivers/crypto/chelsio/chtls/chtls_io.c
index 1e0cc96306dd7..2c1f3ddb0cc79 100644
--- a/drivers/crypto/chelsio/chtls/chtls_io.c
+++ b/drivers/crypto/chelsio/chtls/chtls_io.c
@@ -1449,7 +1449,7 @@ static int chtls_pt_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
csk->wr_max_credits))
sk->sk_write_space(sk);

- if (copied >= target && !sk->sk_backlog.tail)
+ if (copied >= target && !READ_ONCE(sk->sk_backlog.tail))
break;

if (copied) {
@@ -1482,7 +1482,7 @@ static int chtls_pt_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
break;
}
}
- if (sk->sk_backlog.tail) {
+ if (READ_ONCE(sk->sk_backlog.tail)) {
release_sock(sk);
lock_sock(sk);
chtls_cleanup_rbuf(sk, copied);
@@ -1627,7 +1627,7 @@ static int peekmsg(struct sock *sk, struct msghdr *msg,
break;
}

- if (sk->sk_backlog.tail) {
+ if (READ_ONCE(sk->sk_backlog.tail)) {
/* Do not sleep, just process backlog. */
release_sock(sk);
lock_sock(sk);
@@ -1759,7 +1759,7 @@ int chtls_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
csk->wr_max_credits))
sk->sk_write_space(sk);

- if (copied >= target && !sk->sk_backlog.tail)
+ if (copied >= target && !READ_ONCE(sk->sk_backlog.tail))
break;

if (copied) {
@@ -1790,7 +1790,7 @@ int chtls_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
}
}

- if (sk->sk_backlog.tail) {
+ if (READ_ONCE(sk->sk_backlog.tail)) {
release_sock(sk);
lock_sock(sk);
chtls_cleanup_rbuf(sk, copied);
diff --git a/include/net/sock.h b/include/net/sock.h
index 77f36257cac97..bc752237dff3f 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -900,11 +900,11 @@ static inline void __sk_add_backlog(struct sock *sk, struct sk_buff *skb)
skb_dst_force(skb);

if (!sk->sk_backlog.tail)
- sk->sk_backlog.head = skb;
+ WRITE_ONCE(sk->sk_backlog.head, skb);
else
sk->sk_backlog.tail->next = skb;

- sk->sk_backlog.tail = skb;
+ WRITE_ONCE(sk->sk_backlog.tail, skb);
skb->next = NULL;
}

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 616ff2970f4fc..4ce3397e6fcf7 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2038,7 +2038,7 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,

/* Well, if we have backlog, try to process it now yet. */

- if (copied >= target && !sk->sk_backlog.tail)
+ if (copied >= target && !READ_ONCE(sk->sk_backlog.tail))
break;

if (copied) {
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 6ead3c39f3566..bcba579e292ff 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -785,7 +785,7 @@ static int llc_ui_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
}
/* Well, if we have backlog, try to process it now yet. */

- if (copied >= target && !sk->sk_backlog.tail)
+ if (copied >= target && !READ_ONCE(sk->sk_backlog.tail))
break;

if (copied) {
--
2.25.1

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