syzbot


WARNING: suspicious RCU usage in vxlan_xmit

Status: fixed on 2021/11/10 00:50
Reported-by: syzbot+@syzkaller.appspotmail.com
Fix commit: 85e8b032d6eb vxlan: add missing rcu_read_lock() in neigh_reduce()
First crash: 594d, last: 594d

Cause bisection: failed (bisect log)
similar bugs (1):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 WARNING: suspicious RCU usage in vxlan_xmit C done 1 577d 577d 1/1 fixed on 2021/08/06 16:37

Sample crash report:
=============================
WARNING: suspicious RCU usage
5.13.0-rc6-syzkaller #0 Not tainted
-----------------------------
include/net/addrconf.h:313 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
3 locks held by kworker/0:0/5:
 #0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
 #0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
 #0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:617 [inline]
 #0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0: ffff888011064d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x871/0x1600 kernel/workqueue.c:2247
 #1: ffffc90000ca7da8 ((work_completion)(&port->wq)){+.+.}-{0:0}, at: process_one_work+0x8a5/0x1600 kernel/workqueue.c:2251
 #2: ffffffff8bf795c0 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x1da/0x3130 net/core/dev.c:4180

stack backtrace:
CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 5.13.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events ipvlan_process_multicast
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 __in6_dev_get include/net/addrconf.h:313 [inline]
 __in6_dev_get include/net/addrconf.h:311 [inline]
 neigh_reduce drivers/net/vxlan.c:2167 [inline]
 vxlan_xmit+0x34d5/0x4c30 drivers/net/vxlan.c:2919
 __netdev_start_xmit include/linux/netdevice.h:4944 [inline]
 netdev_start_xmit include/linux/netdevice.h:4958 [inline]
 xmit_one net/core/dev.c:3654 [inline]
 dev_hard_start_xmit+0x1eb/0x920 net/core/dev.c:3670
 __dev_queue_xmit+0x2133/0x3130 net/core/dev.c:4246
 ipvlan_process_multicast+0xa99/0xd70 drivers/net/ipvlan/ipvlan_core.c:287
 process_one_work+0x98d/0x1600 kernel/workqueue.c:2276
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2422
 kthread+0x3b1/0x4a0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets Title
ci-upstream-net-this-kasan-gce 2021/06/21 06:06 net dda2626b86c2 aba2b2fb .config console log report syz C WARNING: suspicious RCU usage in vxlan_xmit
* Struck through repros no longer work on HEAD.