From 3065fa2cdd7a66228fcb2cf7f0bded4011c6ca1c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 11 Oct 2023 10:24:29 +0000 Subject: [PATCH] xfrm: fix a data-race in xfrm_lookup_with_ifid() commit de5724ca38fd5e442bae9c1fab31942b6544012d upstream. syzbot complains about a race in xfrm_lookup_with_ifid() [1] When preparing commit 0a9e5794b21e ("xfrm: annotate data-race around use_time") I thought xfrm_lookup_with_ifid() was modifying a still private structure. [1] BUG: KCSAN: data-race in xfrm_lookup_with_ifid / xfrm_lookup_with_ifid write to 0xffff88813ea41108 of 8 bytes by task 8150 on cpu 1: xfrm_lookup_with_ifid+0xce7/0x12d0 net/xfrm/xfrm_policy.c:3218 xfrm_lookup net/xfrm/xfrm_policy.c:3270 [inline] xfrm_lookup_route+0x3b/0x100 net/xfrm/xfrm_policy.c:3281 ip6_dst_lookup_flow+0x98/0xc0 net/ipv6/ip6_output.c:1246 send6+0x241/0x3c0 drivers/net/wireguard/socket.c:139 wg_socket_send_skb_to_peer+0xbd/0x130 drivers/net/wireguard/socket.c:178 wg_socket_send_buffer_to_peer+0xd6/0x100 drivers/net/wireguard/socket.c:200 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline] wg_packet_handshake_send_worker+0x10c/0x150 drivers/net/wireguard/send.c:51 process_one_work kernel/workqueue.c:2630 [inline] process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703 worker_thread+0x525/0x730 kernel/workqueue.c:2784 kthread+0x1d7/0x210 kernel/kthread.c:388 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304 write to 0xffff88813ea41108 of 8 bytes by task 15867 on cpu 0: xfrm_lookup_with_ifid+0xce7/0x12d0 net/xfrm/xfrm_policy.c:3218 xfrm_lookup net/xfrm/xfrm_policy.c:3270 [inline] xfrm_lookup_route+0x3b/0x100 net/xfrm/xfrm_policy.c:3281 ip6_dst_lookup_flow+0x98/0xc0 net/ipv6/ip6_output.c:1246 send6+0x241/0x3c0 drivers/net/wireguard/socket.c:139 wg_socket_send_skb_to_peer+0xbd/0x130 drivers/net/wireguard/socket.c:178 wg_socket_send_buffer_to_peer+0xd6/0x100 drivers/net/wireguard/socket.c:200 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline] wg_packet_handshake_send_worker+0x10c/0x150 drivers/net/wireguard/send.c:51 process_one_work kernel/workqueue.c:2630 [inline] process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703 worker_thread+0x525/0x730 kernel/workqueue.c:2784 kthread+0x1d7/0x210 kernel/kthread.c:388 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304 value changed: 0x00000000651cd9d1 -> 0x00000000651cd9d2 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 15867 Comm: kworker/u4:58 Not tainted 6.6.0-rc4-syzkaller-00016-g5e62ed3b1c8a #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023 Workqueue: wg-kex-wg2 wg_packet_handshake_send_worker Fixes: 0a9e5794b21e ("xfrm: annotate data-race around use_time") Reported-by: syzbot Signed-off-by: Eric Dumazet Cc: Steffen Klassert Signed-off-by: Steffen Klassert Signed-off-by: Greg Kroah-Hartman --- net/xfrm/xfrm_policy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index e65de78cb61b..8c990becf4f6 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -3138,7 +3138,7 @@ struct dst_entry *xfrm_lookup_with_ifid(struct net *net, } for (i = 0; i < num_pols; i++) - pols[i]->curlft.use_time = ktime_get_real_seconds(); + WRITE_ONCE(pols[i]->curlft.use_time, ktime_get_real_seconds()); if (num_xfrms < 0) { /* Prohibit the flow */