From: Eric Dumazet edumazet@google.com
commit 90b2be27bb0e56483f335cc10fb59ec66882b949 upstream.
KCSAN reported the following race [1]
BUG: KCSAN: data-race in __dev_queue_xmit / net_tx_action
read to 0xffff8880ba403508 of 1 bytes by task 21814 on cpu 1: __dev_xmit_skb net/core/dev.c:3389 [inline] __dev_queue_xmit+0x9db/0x1b40 net/core/dev.c:3761 dev_queue_xmit+0x21/0x30 net/core/dev.c:3825 neigh_hh_output include/net/neighbour.h:500 [inline] neigh_output include/net/neighbour.h:509 [inline] ip6_finish_output2+0x873/0xec0 net/ipv6/ip6_output.c:116 __ip6_finish_output net/ipv6/ip6_output.c:142 [inline] __ip6_finish_output+0x2d7/0x330 net/ipv6/ip6_output.c:127 ip6_finish_output+0x41/0x160 net/ipv6/ip6_output.c:152 NF_HOOK_COND include/linux/netfilter.h:294 [inline] ip6_output+0xf2/0x280 net/ipv6/ip6_output.c:175 dst_output include/net/dst.h:436 [inline] ip6_local_out+0x74/0x90 net/ipv6/output_core.c:179 ip6_send_skb+0x53/0x110 net/ipv6/ip6_output.c:1795 udp_v6_send_skb.isra.0+0x3ec/0xa70 net/ipv6/udp.c:1173 udpv6_sendmsg+0x1906/0x1c20 net/ipv6/udp.c:1471 inet6_sendmsg+0x6d/0x90 net/ipv6/af_inet6.c:576 sock_sendmsg_nosec net/socket.c:637 [inline] sock_sendmsg+0x9f/0xc0 net/socket.c:657 ___sys_sendmsg+0x2b7/0x5d0 net/socket.c:2311 __sys_sendmmsg+0x123/0x350 net/socket.c:2413 __do_sys_sendmmsg net/socket.c:2442 [inline] __se_sys_sendmmsg net/socket.c:2439 [inline] __x64_sys_sendmmsg+0x64/0x80 net/socket.c:2439 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x44/0xa9
write to 0xffff8880ba403508 of 1 bytes by interrupt on cpu 0: qdisc_run_begin include/net/sch_generic.h:160 [inline] qdisc_run include/net/pkt_sched.h:120 [inline] net_tx_action+0x2b1/0x6c0 net/core/dev.c:4551 __do_softirq+0x115/0x33f kernel/softirq.c:292 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1082 do_softirq.part.0+0x6b/0x80 kernel/softirq.c:337 do_softirq kernel/softirq.c:329 [inline] __local_bh_enable_ip+0x76/0x80 kernel/softirq.c:189 local_bh_enable include/linux/bottom_half.h:32 [inline] rcu_read_unlock_bh include/linux/rcupdate.h:688 [inline] ip6_finish_output2+0x7bb/0xec0 net/ipv6/ip6_output.c:117 __ip6_finish_output net/ipv6/ip6_output.c:142 [inline] __ip6_finish_output+0x2d7/0x330 net/ipv6/ip6_output.c:127 ip6_finish_output+0x41/0x160 net/ipv6/ip6_output.c:152 NF_HOOK_COND include/linux/netfilter.h:294 [inline] ip6_output+0xf2/0x280 net/ipv6/ip6_output.c:175 dst_output include/net/dst.h:436 [inline] ip6_local_out+0x74/0x90 net/ipv6/output_core.c:179 ip6_send_skb+0x53/0x110 net/ipv6/ip6_output.c:1795 udp_v6_send_skb.isra.0+0x3ec/0xa70 net/ipv6/udp.c:1173 udpv6_sendmsg+0x1906/0x1c20 net/ipv6/udp.c:1471 inet6_sendmsg+0x6d/0x90 net/ipv6/af_inet6.c:576 sock_sendmsg_nosec net/socket.c:637 [inline] sock_sendmsg+0x9f/0xc0 net/socket.c:657 ___sys_sendmsg+0x2b7/0x5d0 net/socket.c:2311 __sys_sendmmsg+0x123/0x350 net/socket.c:2413 __do_sys_sendmmsg net/socket.c:2442 [inline] __se_sys_sendmmsg net/socket.c:2439 [inline] __x64_sys_sendmmsg+0x64/0x80 net/socket.c:2439 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: 21817 Comm: syz-executor.2 Not tainted 5.4.0-rc6+ #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Fixes: d518d2ed8640 ("net/sched: fix race between deactivation and dequeue for NOLOCK qdisc") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Cc: Paolo Abeni pabeni@redhat.com Cc: Davide Caratti dcaratti@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/net/sch_generic.h | 6 +++--- net/core/dev.c | 2 +- net/sched/sch_generic.c | 2 +- 3 files changed, 5 insertions(+), 5 deletions(-)
--- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -149,8 +149,8 @@ static inline bool qdisc_is_percpu_stats static inline bool qdisc_is_empty(const struct Qdisc *qdisc) { if (qdisc_is_percpu_stats(qdisc)) - return qdisc->empty; - return !qdisc->q.qlen; + return READ_ONCE(qdisc->empty); + return !READ_ONCE(qdisc->q.qlen); }
static inline bool qdisc_run_begin(struct Qdisc *qdisc) @@ -158,7 +158,7 @@ static inline bool qdisc_run_begin(struc if (qdisc->flags & TCQ_F_NOLOCK) { if (!spin_trylock(&qdisc->seqlock)) return false; - qdisc->empty = false; + WRITE_ONCE(qdisc->empty, false); } else if (qdisc_is_running(qdisc)) { return false; } --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3386,7 +3386,7 @@ static inline int __dev_xmit_skb(struct qdisc_calculate_pkt_len(skb, q);
if (q->flags & TCQ_F_NOLOCK) { - if ((q->flags & TCQ_F_CAN_BYPASS) && q->empty && + if ((q->flags & TCQ_F_CAN_BYPASS) && READ_ONCE(q->empty) && qdisc_run_begin(q)) { if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) { --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -657,7 +657,7 @@ static struct sk_buff *pfifo_fast_dequeu if (likely(skb)) { qdisc_update_stats_at_dequeue(qdisc, skb); } else { - qdisc->empty = true; + WRITE_ONCE(qdisc->empty, true); }
return skb;