Subject: Re: WARNING in mark_chain_precision

From: syzbot <[email-masked]>
Date: Mon, 08 Jul 2019 21:25:00 -0700

Hello,

syzbot has tested the proposed patch but the reproducer still triggered  
crash:
WARNING in bpf_jit_free

WARNING: CPU: 0 PID: 9077 at kernel/bpf/core.c:851 bpf_jit_free+0x157/0x1b0
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 9077 Comm: kworker/0:3 Not tainted 5.2.0-rc6+ #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events bpf_prog_free_deferred
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  panic+0x2cb/0x744 kernel/panic.c:219
  __warn.cold+0x20/0x4d kernel/panic.c:576
  report_bug+0x263/0x2b0 lib/bug.c:186
  fixup_bug arch/x86/kernel/traps.c:179 [inline]
  fixup_bug arch/x86/kernel/traps.c:174 [inline]
  do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
  do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:986
RIP: 0010:bpf_jit_free+0x157/0x1b0
Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 5d 48 b8 00 02 00 00  
00 00 ad de 48 39 43 70 0f 84 05 ff ff ff e8 09 7f f4 ff <0f> 0b e9 f9 fe  
ff ff e8 2d 02 2e 00 e9 d9 fe ff ff 48 89 7d e0 e8
RSP: 0018:ffff888084affcb0 EFLAGS: 00010293
RAX: ffff88808a622100 RBX: ffff88809639d580 RCX: ffffffff817b0b0d
RDX: 0000000000000000 RSI: ffffffff817c4557 RDI: ffff88809639d5f0
RBP: ffff888084affcd0 R08: 1ffffffff150daa8 R09: fffffbfff150daa9
R10: fffffbfff150daa8 R11: ffffffff8a86d547 R12: ffffc90001921000
R13: ffff88809639d5e8 R14: ffff8880a0589800 R15: ffff8880ae834d40
  bpf_prog_free_deferred+0x27a/0x350 kernel/bpf/core.c:1982
  process_one_work+0x989/0x1790 kernel/workqueue.c:2269
  worker_thread+0x98/0xe40 kernel/workqueue.c:2415
  kthread+0x354/0x420 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..

Tested on:

commit:         b9321614 bpf: fix precision bit propagation for BPF_ST ins..
git tree:       https://github.com/anakryiko/linux bpf-fix-precise-bpf_st
console output: https://syzkaller.appspot.com/x/log.txt?x=112f0dfda00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6bb3e6e7997c14f9
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)