Re: WARNING in tracepoint_add_func

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    325d0eab Merge branch 'akpm' (patches from Andrew)
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16992c81900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b12e84189082991c
dashboard link: https://syzkaller.appspot.com/bug?extid=721aa903751db87aa244
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17c797b5900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10569c03900000

The issue was bisected to:

commit 58956317c8de52009d1a38a721474c24aef74fe7
Author: David Ahern <dsahern@xxxxxxxxx>
Date:   Fri Dec 7 20:24:57 2018 +0000

    neighbor: Improve garbage collection

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=146ba853900000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=166ba853900000
console output: https://syzkaller.appspot.com/x/log.txt?x=126ba853900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+721aa903751db87aa244@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 58956317c8de ("neighbor: Improve garbage collection")

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WARNING: CPU: 1 PID: 6872 at kernel/tracepoint.c:243 tracepoint_add_func+0x254/0x880 kernel/tracepoint.c:243
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 6872 Comm: syz-executor482 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 panic+0x382/0x7fb kernel/panic.c:231
 __warn.cold+0x20/0x4b kernel/panic.c:600
 report_bug+0x1bd/0x210 lib/bug.c:198
 handle_bug+0x38/0x90 arch/x86/kernel/traps.c:234
 exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:254
 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:536
RIP: 0010:tracepoint_add_func+0x254/0x880 kernel/tracepoint.c:243
Code: 44 24 20 48 8b 5b 08 80 38 00 0f 85 6b 05 00 00 48 8b 44 24 08 48 3b 58 08 0f 85 2d ff ff ff 41 bc ef ff ff ff e8 ec 62 fe ff <0f> 0b e8 e5 62 fe ff 44 89 e0 48 83 c4 38 5b 5d 41 5c 41 5d 41 5e
RSP: 0000:ffffc900060f7ac0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffc90000e76000 RCX: ffffffff8177dc72
RDX: ffff888096766000 RSI: ffffffff8177dcd4 RDI: ffff8880a6b2ec48
RBP: ffffffff8213fae0 R08: 0000000000000000 R09: ffffffff8a0c176b
R10: 000000000000000a R11: 0000000000000000 R12: 00000000ffffffef
R13: 0000000000000002 R14: dffffc0000000000 R15: ffff8880a6b2ec10
 tracepoint_probe_register_prio kernel/tracepoint.c:315 [inline]
 tracepoint_probe_register+0x9c/0xe0 kernel/tracepoint.c:335
 __bpf_probe_register kernel/trace/bpf_trace.c:1950 [inline]
 bpf_probe_register+0x16c/0x1d0 kernel/trace/bpf_trace.c:1955
 bpf_raw_tracepoint_open+0x34e/0xb20 kernel/bpf/syscall.c:2741
 __do_sys_bpf+0x1b2f/0x4c60 kernel/bpf/syscall.c:4220
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4415a9
Code: e8 ac e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 8b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc28dd5d08 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004415a9
RDX: 0000000000000010 RSI: 0000000020000040 RDI: 0000000000000011
RBP: 0000000000010308 R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000004 R11: 0000000000000246 R12: 00000000004023c0
R13: 0000000000402450 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..