bisecting fixing commit since ba4f184e126b751d1bffad5897f263108befc780
building syzkaller on 9e1fa68ee1625a7f0ef03906ee1abb40cb987fbf
testing commit ba4f184e126b751d1bffad5897f263108befc780 with gcc (GCC) 8.4.1 20210217
kernel signature: 3002effa8e8a479db947239df63ae9824b906c1f236ac3f505d93e797768a0ba
all runs: crashed: WARNING: refcount bug in qrtr_node_lookup
testing current HEAD a96bfed64c8986d6404e553f18203cae1f5ac7e6
testing commit a96bfed64c8986d6404e553f18203cae1f5ac7e6 with gcc (GCC) 10.2.1 20210217
kernel signature: 62205c5f8f1af22d1ee3c945a3af7c964c60a9c8b8df897c86ec16fc18cf15d2
all runs: crashed: WARNING: refcount bug in qrtr_recvmsg
revisions tested: 2, total time: 24m58.220524751s (build: 12m53.892243501s, test: 11m11.437314772s)
the crash still happens on HEAD
commit msg: Merge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm
crash: WARNING: refcount bug in qrtr_recvmsg
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 196 at lib/refcount.c:25 refcount_warn_saturate+0x120/0x190 lib/refcount.c:25
Modules linked in:
CPU: 0 PID: 196 Comm: kworker/u4:5 Not tainted 5.13.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: qrtr_ns_handler qrtr_ns_worker
RIP: 0010:refcount_warn_saturate+0x120/0x190 lib/refcount.c:25
Code: 1d 9e fe f1 07 80 fb 01 0f 87 e0 25 17 04 83 e3 01 0f 85 5d ff ff ff 48 c7 c7 20 d2 78 88 c6 05 7e fe f1 07 01 e8 b6 44 06 04 <0f> 0b e9 43 ff ff ff 0f b6 1d 68 fe f1 07 80 fb 01 0f 87 d5 25 17
RSP: 0018:ffffc90000b57a30 EFLAGS: 00010082
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000002 RSI: 0000000000000004 RDI: fffff5200016af38
RBP: 0000000000000002 R08: 0000000000000001 R09: ffff8881f622095b
R10: ffffed103ec4412b R11: 746e756f63666572 R12: ffff8881220be474
R13: ffff8881220be470 R14: 0000000000000282 R15: ffff88812c138000
FS:  0000000000000000(0000) GS:ffff8881f6200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000533198 CR3: 00000001183ca004 CR4: 00000000001706f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __refcount_add include/linux/refcount.h:199 [inline]
 __refcount_inc include/linux/refcount.h:250 [inline]
 refcount_inc include/linux/refcount.h:267 [inline]
 kref_get include/linux/kref.h:45 [inline]
 qrtr_node_acquire net/qrtr/qrtr.c:202 [inline]
 qrtr_node_lookup net/qrtr/qrtr.c:398 [inline]
 qrtr_send_resume_tx net/qrtr/qrtr.c:995 [inline]
 qrtr_recvmsg+0x75a/0x850 net/qrtr/qrtr.c:1063
 qrtr_ns_worker+0x14c/0x1260 net/qrtr/ns.c:684
 process_one_work+0x84c/0x13d0 kernel/workqueue.c:2276
 worker_thread+0x598/0xf80 kernel/workqueue.c:2422
 kthread+0x36f/0x450 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
irq event stamp: 3911390
hardirqs last  enabled at (3911389): [<ffffffff87c93740>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
hardirqs last  enabled at (3911389): [<ffffffff87c93740>] _raw_spin_unlock_irqrestore+0x40/0x90 kernel/locking/spinlock.c:191
hardirqs last disabled at (3911390): [<ffffffff87c934e9>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]
hardirqs last disabled at (3911390): [<ffffffff87c934e9>] _raw_spin_lock_irqsave+0xa9/0xd0 kernel/locking/spinlock.c:159
softirqs last  enabled at (3911386): [<ffffffff85e3e9e1>] lock_sock_nested+0x81/0xf0 net/core/sock.c:3068
softirqs last disabled at (3911384): [<ffffffff85e3e999>] spin_lock_bh include/linux/spinlock.h:359 [inline]
softirqs last disabled at (3911384): [<ffffffff85e3e999>] lock_sock_nested+0x39/0xf0 net/core/sock.c:3065
---[ end trace 35cc74d6fce09f45 ]---