netdev - Re: [syzbot] [net?] WARNING in xfrm_state

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Message-ID: <aIisBdRAM2vZ_VCW@krikkit>
Date: Tue, 29 Jul 2025 13:09:57 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: Steffen Klassert <steffen.klassert@...unet.com>
Cc: syzbot <syzbot+6641a61fe0e2e89ae8c5@...kaller.appspotmail.com>,
	davem@...emloft.net, edumazet@...gle.com,
	herbert@...dor.apana.org.au, horms@...nel.org, kuba@...nel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] WARNING in xfrm_state_fini (3)

Hi Steffen,

2025-07-29, 13:01:22 +0200, Steffen Klassert wrote:
> On Tue, Jul 29, 2025 at 12:08:31AM -0700, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following issue on:
> > 
> > HEAD commit:    038d61fd6422 Linux 6.16
> > git tree:       upstream
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=11b88cf0580000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=4066f1c76cfbc4fe
> > dashboard link: https://syzkaller.appspot.com/bug?extid=6641a61fe0e2e89ae8c5
> > compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16ca1782580000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=140194a2580000
> > 
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/6505c612be11/disk-038d61fd.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/e466ef29c1ca/vmlinux-038d61fd.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/b6d3d8fc5cbb/bzImage-038d61fd.xz
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+6641a61fe0e2e89ae8c5@...kaller.appspotmail.com
> > 
> > ------------[ cut here ]------------
> > WARNING: CPU: 1 PID: 36 at net/xfrm/xfrm_state.c:3284 xfrm_state_fini+0x270/0x2f0 net/xfrm/xfrm_state.c:3284
> > Modules linked in:
> > CPU: 1 UID: 0 PID: 36 Comm: kworker/u8:2 Not tainted 6.16.0-syzkaller #0 PREEMPT(full) 
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
> > Workqueue: netns cleanup_net
> > RIP: 0010:xfrm_state_fini+0x270/0x2f0 net/xfrm/xfrm_state.c:3284
> > Code: c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 68 fa 0b f8 48 8b 3b 5b 41 5c 41 5d 41 5e 41 5f 5d e9 56 c8 ec f7 e8 51 e8 a9 f7 90 <0f> 0b 90 e9 fd fd ff ff e8 43 e8 a9 f7 90 0f 0b 90 e9 60 fe ff ff
> > RSP: 0018:ffffc90000ac7898 EFLAGS: 00010293
> > RAX: ffffffff8a163e8f RBX: ffff888034008000 RCX: ffff888143299e00
> > RDX: 0000000000000000 RSI: ffffffff8db8419f RDI: ffff888143299e00
> > RBP: ffffc90000ac79b0 R08: ffffffff8f6196e7 R09: 1ffffffff1ec32dc
> > R10: dffffc0000000000 R11: fffffbfff1ec32dd R12: ffffffff8f617760
> > R13: 1ffff92000158f40 R14: ffff8880340094c0 R15: dffffc0000000000
> > FS:  0000000000000000(0000) GS:ffff888125d23000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007fbd9e960960 CR3: 00000000316d3000 CR4: 0000000000350ef0
> > Call Trace:
> >  <TASK>
> >  xfrm_net_exit+0x2d/0x70 net/xfrm/xfrm_policy.c:4348
> >  ops_exit_list net/core/net_namespace.c:200 [inline]
> >  ops_undo_list+0x49a/0x990 net/core/net_namespace.c:253
> >  cleanup_net+0x4c5/0x800 net/core/net_namespace.c:686
> >  process_one_work kernel/workqueue.c:3238 [inline]
> >  process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
> >  worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
> >  kthread+0x711/0x8a0 kernel/kthread.c:464
> >  ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> >  </TASK>
> 
> Hi Sabrina, your recent ipcomp patches seem to trigger this issue.
> At least reverting them make it go away. Can you please look
> into this?

I haven't looked at the other reports yet, but this one seems to be a
stupid mistake in my revert patch. With these changes, the syzbot
repro stops splatting here:


#syz test

diff --git a/net/ipv6/xfrm6_tunnel.c b/net/ipv6/xfrm6_tunnel.c
index 5120a763da0d..0a0eeaed0591 100644
--- a/net/ipv6/xfrm6_tunnel.c
+++ b/net/ipv6/xfrm6_tunnel.c
@@ -334,7 +334,7 @@ static void __net_exit xfrm6_tunnel_net_exit(struct net *net)
 	struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);
 	unsigned int i;
 
-	xfrm_state_flush(net, IPSEC_PROTO_ANY, false);
+	xfrm_state_flush(net, 0, false);
 	xfrm_flush_gc();
 
 	for (i = 0; i < XFRM6_TUNNEL_SPI_BYADDR_HSIZE; i++)
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 97ff756191ba..5f1da305eea8 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -3278,7 +3278,7 @@ void xfrm_state_fini(struct net *net)
 	unsigned int sz;
 
 	flush_work(&net->xfrm.state_hash_work);
-	xfrm_state_flush(net, IPSEC_PROTO_ANY, false);
+	xfrm_state_flush(net, 0, false);
 	flush_work(&xfrm_state_gc_work);
 
 	WARN_ON(!list_empty(&net->xfrm.state_all));


-- 
Sabrina