WARNING: refcount bug in do_enable_set

WARNING: refcount bug in do_enable_set

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    8f3d9f35 Linux 5.7-rc1
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1182b24fe00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=11f10cc27c63cade
dashboard link: https://syzkaller.appspot.com/bug?extid=2e9900a1e1b3c9c96a77
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2e9900a1e1b3c9c96a77@syzkaller.appspotmail.com

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 10817 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 10817 Comm: kworker/0:7 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events do_enable_set
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1e9/0x30e lib/dump_stack.c:118
 panic+0x264/0x7a0 kernel/panic.c:221
 __warn+0x209/0x210 kernel/panic.c:582
 report_bug+0x1ac/0x2d0 lib/bug.c:195
 fixup_bug arch/x86/kernel/traps.c:175 [inline]
 do_error_trap+0xca/0x1c0 arch/x86/kernel/traps.c:267
 do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Code: c7 9a a9 f2 88 31 c0 e8 a3 fb ac fd 0f 0b eb 85 e8 5a e7 da fd c6 05 10 48 cf 05 01 48 c7 c7 c6 a9 f2 88 31 c0 e8 85 fb ac fd <0f> 0b e9 64 ff ff ff e8 39 e7 da fd c6 05 f0 47 cf 05 01 48 c7 c7
RSP: 0000:ffffc900016d7c48 EFLAGS: 00010246
RAX: 8e9964d9ee901300 RBX: 0000000000000003 RCX: ffff888089a0e5c0
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: ffffffff815cbca9 R09: ffffed1015d06660
R10: ffffed1015d06660 R11: 0000000000000000 R12: ffffffff895f43c8
R13: dffffc0000000000 R14: ffff88809365b018 R15: ffff8880ae83b400
 do_enable_set+0x63a/0x8d0 net/bluetooth/6lowpan.c:1075
 process_one_work+0x76e/0xfd0 kernel/workqueue.c:2268
 worker_thread+0xa7f/0x1450 kernel/workqueue.c:2414
 kthread+0x353/0x380 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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Re: WARNING: refcount bug in do_enable_set

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    ac3a0c84 Merge git://git.kernel.org/pub/scm/linux/kernel/g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1194935c900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e59ee776d5aa8d55
dashboard link: https://syzkaller.appspot.com/bug?extid=2e9900a1e1b3c9c96a77
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10b7ddca900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=126dcf6c900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2e9900a1e1b3c9c96a77@syzkaller.appspotmail.com

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 2540 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 2540 Comm: kworker/1:8 Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events do_enable_set
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1f0/0x31e lib/dump_stack.c:118
 panic+0x264/0x7a0 kernel/panic.c:231
 __warn+0x227/0x250 kernel/panic.c:600
 report_bug+0x1b1/0x2e0 lib/bug.c:198
 handle_bug+0x42/0x80 arch/x86/kernel/traps.c:235
 exc_invalid_op+0x16/0x40 arch/x86/kernel/traps.c:255
 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:540
RIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Code: c7 8a af 14 89 31 c0 e8 b3 f2 a8 fd 0f 0b eb 85 e8 2a 32 d7 fd c6 05 a4 d9 eb 05 01 48 c7 c7 b6 af 14 89 31 c0 e8 95 f2 a8 fd <0f> 0b e9 64 ff ff ff e8 09 32 d7 fd c6 05 84 d9 eb 05 01 48 c7 c7
RSP: 0018:ffffc90007d27c48 EFLAGS: 00010246
RAX: adb9104953f59b00 RBX: 0000000000000003 RCX: ffff8880a02d0540
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: ffffffff815dd389 R09: ffffed1015d262c0
R10: ffffed1015d262c0 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880a0259118 R14: dffffc0000000000 R15: ffff8880ae9350c0
 do_enable_set+0x66e/0x900 net/bluetooth/6lowpan.c:1083
 process_one_work+0x789/0xfc0 kernel/workqueue.c:2269
 worker_thread+0xaa4/0x1460 kernel/workqueue.c:2415
 kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
Kernel Offset: disabled
Rebooting in 86400 seconds..

Re: WARNING: refcount bug in do_enable_set

[syzbot]

syzbot suspects this issue was fixed by commit:

commit b83764f9220a4a14525657466f299850bbc98de9
Author: Miao-chen Chou <mcchou@chromium.org>
Date:   Tue Jun 30 03:15:00 2020 +0000

    Bluetooth: Fix kernel oops triggered by hci_adv_monitors_clear()

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=115a4245900000
start commit:   fffe3ae0 Merge tag 'for-linus-hmm' of git://git.kernel.org..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=226c7a97d80bec54
dashboard link: https://syzkaller.appspot.com/bug?extid=2e9900a1e1b3c9c96a77
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12b3efea900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11131284900000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: Bluetooth: Fix kernel oops triggered by hci_adv_monitors_clear()

For information about bisection process see: https://goo.gl/tpsmEJ#bisection