netdev - Re: [PATCH net] xfrm: fix a data-race in xfrm_lookup_with

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Message-ID: <20231013152225.GL29570@kernel.org>
Date: Fri, 13 Oct 2023 17:22:25 +0200
From: Simon Horman <horms@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, eric.dumazet@...il.com,
	syzbot <syzkaller@...glegroups.com>,
	Steffen Klassert <steffen.klassert@...unet.com>
Subject: Re: [PATCH net] xfrm: fix a data-race in xfrm_lookup_with_ifid()

On Wed, Oct 11, 2023 at 10:24:29AM +0000, Eric Dumazet wrote:
> 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 <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Steffen Klassert <steffen.klassert@...unet.com>

Reviewed-by: Simon Horman <horms@...nel.org>