Re: [syzbot] [net?] WARNING in __linkwatch_sync_dev (2)

[Stanislav Fomichev <stfomichev@gmail.com>]

On 06/13, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    27605c8c0f69 Merge tag 'net-6.16-rc2' of git://git.kernel...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17bb9d70580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8e5a54165d499a9
> dashboard link: https://syzkaller.appspot.com/bug?extid=b8c48ea38ca27d150063
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11a7b9d4580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1421310c580000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-27605c8c.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/ab939a8a93b4/vmlinux-27605c8c.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e90d45016aac/bzImage-27605c8c.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b8c48ea38ca27d150063@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> RTNL: assertion failed at ./include/net/netdev_lock.h (72)
> WARNING: CPU: 2 PID: 60 at ./include/net/netdev_lock.h:72 netdev_ops_assert_locked include/net/netdev_lock.h:72 [inline]
> WARNING: CPU: 2 PID: 60 at ./include/net/netdev_lock.h:72 __linkwatch_sync_dev+0x1ed/0x230 net/core/link_watch.c:279
> Modules linked in:
> CPU: 2 UID: 0 PID: 60 Comm: kworker/u32:3 Not tainted 6.16.0-rc1-syzkaller-00101-g27605c8c0f69 #0 PREEMPT(full) 
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> Workqueue: bond0 bond_mii_monitor
> RIP: 0010:netdev_ops_assert_locked include/net/netdev_lock.h:72 [inline]
> RIP: 0010:__linkwatch_sync_dev+0x1ed/0x230 net/core/link_watch.c:279
> Code: 05 ff ff ff e8 94 b6 59 f8 c6 05 e9 0f 2e 07 01 90 ba 48 00 00 00 48 c7 c6 c0 8c e3 8c 48 c7 c7 60 8c e3 8c e8 94 7b 18 f8 90 <0f> 0b 90 90 e9 d6 fe ff ff 48 c7 c7 44 3b a8 90 e8 ae 86 c0 f8 e9
> RSP: 0018:ffffc90000ce79f0 EFLAGS: 00010286
> RAX: 0000000000000000 RBX: ffff8880363a2000 RCX: ffffffff817ae368
> RDX: ffff888022148000 RSI: ffffffff817ae375 RDI: 0000000000000001
> RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000001 R12: 1ffff9200019cf48
> R13: ffff8880363a2cc5 R14: ffffffff8c5909c0 R15: ffffffff899ba310
> FS:  0000000000000000(0000) GS:ffff8880d6954000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ffd4122af9c CR3: 000000000e382000 CR4: 0000000000352ef0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  ethtool_op_get_link+0x1d/0x70 net/ethtool/ioctl.c:63
>  bond_check_dev_link+0x3f9/0x710 drivers/net/bonding/bond_main.c:863
>  bond_miimon_inspect drivers/net/bonding/bond_main.c:2745 [inline]
>  bond_mii_monitor+0x3c0/0x2dc0 drivers/net/bonding/bond_main.c:2967
>  process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
>  process_scheduled_works kernel/workqueue.c:3321 [inline]
>  worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
>  kthread+0x3c5/0x780 kernel/kthread.c:464
>  ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>  </TASK>
> 
> 
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.

#syz test

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index c4d53e8e7c15..e2c4bcdb8b1a 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2739,7 +2739,7 @@ static int bond_miimon_inspect(struct bonding *bond)
 			ignore_updelay = true;
 	}
 
-	bond_for_each_slave_rcu(bond, slave, iter) {
+	bond_for_each_slave(bond, slave, iter) {
 		bond_propose_link_state(slave, BOND_LINK_NOCHANGE);
 
 		link_state = bond_check_dev_link(bond, slave->dev, 0);
@@ -2962,35 +2962,28 @@ static void bond_mii_monitor(struct work_struct *work)
 	if (!bond_has_slaves(bond))
 		goto re_arm;
 
-	rcu_read_lock();
+	/* Race avoidance with bond_close cancel of workqueue */
+	if (!rtnl_trylock()) {
+		delay = 1;
+		should_notify_peers = false;
+		goto re_arm;
+	}
+
 	should_notify_peers = bond_should_notify_peers(bond);
 	commit = !!bond_miimon_inspect(bond);
 	if (bond->send_peer_notif) {
-		rcu_read_unlock();
-		if (rtnl_trylock()) {
-			bond->send_peer_notif--;
-			rtnl_unlock();
-		}
-	} else {
-		rcu_read_unlock();
+		bond->send_peer_notif--;
 	}
 
 	if (commit) {
-		/* Race avoidance with bond_close cancel of workqueue */
-		if (!rtnl_trylock()) {
-			delay = 1;
-			should_notify_peers = false;
-			goto re_arm;
-		}
-
 		bond_for_each_slave(bond, slave, iter) {
 			bond_commit_link_state(slave, BOND_SLAVE_NOTIFY_LATER);
 		}
 		bond_miimon_commit(bond);
-
-		rtnl_unlock();	/* might sleep, hold no other locks */
 	}
 
+	rtnl_unlock();	/* might sleep, hold no other locks */
+
 re_arm:
 	if (bond->params.miimon)
 		queue_delayed_work(bond->wq, &bond->mii_work, delay);