From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 60D482D7DE9; Wed, 6 May 2026 16:29:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778084987; cv=none; b=k+YUzxmMuBoOIQ2HIXspOu+VIvQCp8T1x22vrsP/9k5D9wpnztAA6sn/gCh2mV8hFFwJ7UemRBPwQ4rRdJ0hsmWtC5V6IYGEUIn1ApQvk/rzn+ELI5mW8C23P2+VaQjCzS8+u8HVc4Hu0kSUxIDHrwTEjc31ckG2nPXlPiGEh0Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778084987; c=relaxed/simple; bh=KEe+JqSrfEsaB9UFcPMwnZ1iqiFBaRF+JFM1eZblrew=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=OVwIIzWz9m04o5XxXSwFNh9Xv+RqiV+uM3bTQqsd9c2XhV08kzPEkvRf4wQTP9oh4/PoW+2tCGUSVMDSCOKP4oLPtH0+laun9/wZIdnQr+UL2kQEEgRGdnr9mVl0z+HmjWtj28Z+VTq/VBWyf/pI9dHahqTBLAU/oyoVpwyhxqo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=I/NwxZJz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="I/NwxZJz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F6E3C2BCB0; Wed, 6 May 2026 16:29:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778084986; bh=KEe+JqSrfEsaB9UFcPMwnZ1iqiFBaRF+JFM1eZblrew=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=I/NwxZJzB57YK+nhQMlPdHeXES+Gthxkh1V7282yJtp2H1wJ2daegp2cFYRwCKDt+ +m1h3HuYGDrZtkHx2zafe/Z27xUBSzw/1aLqVc8pi93lMLibALJEQLgnayUOYgPocr hc1GMWDwNUu7lvs+3zefmrxTXAO8oI9i+TXZY2tstiwGtr8oGiJkKUmtL+JXovsug9 9+ofhW8jooEBxCLAGBAf3XE3c5avT/bQi17QnA7/ReyKtWlNJFYt/NTAdTtYM1uf1B vi9owbPyAhjdnTtioAFuhYLx6QRizS3crsx2f9ZYP/GRukQIXdF/7HXnBLpwCm3pEG o6M0LHk6tCYBw== From: Thomas Gleixner To: syzbot , linux-kernel@vger.kernel.org, peterz@infradead.org, syzkaller-bugs@googlegroups.com Cc: bridge@lists.linux.dev, Nikolay Aleksandrov , Ido Schimmel , netdev@vger.kernel.org Subject: Re: [syzbot] [kernel?] WARNING: ODEBUG bug in smpboot_thread_fn In-Reply-To: <69f88fc0.050a0220.3460d5.0004.GAE@google.com> References: <69f88fc0.050a0220.3460d5.0004.GAE@google.com> Date: Wed, 06 May 2026 18:29:43 +0200 Message-ID: <87qznowlfs.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Mon, May 04 2026 at 05:23, syzbot wrote: Cc'ed network/bridge people as that's clearly in their realm. > Hello, > > syzbot found the following issue on: > > HEAD commit: 6d35786de281 Merge tag 'for-linus' of git://git.kernel.org.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=126bf21f980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=f2e8ebfec4636d32 > dashboard link: https://syzkaller.appspot.com/bug?extid=ae231e0552fa77b26ea1 > compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/b3ab34c4c807/disk-6d35786d.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/03f465478178/vmlinux-6d35786d.xz > kernel image: https://storage.googleapis.com/syzbot-assets/29d261604425/bzImage-6d35786d.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+ae231e0552fa77b26ea1@syzkaller.appspotmail.com > > ------------[ cut here ]------------ > ODEBUG: free active (active state 0) object: ffff888033a47278 object type: timer_list hint: br_ip6_multicast_port_query_expired+0x0/0x380 net/bridge/br_multicast.c:-1 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ An object which contains an active timer is RCU freed.... > WARNING: lib/debugobjects.c:632 at debug_print_object lib/debugobjects.c:629 [inline], CPU#1: rcuc/1/28 > WARNING: lib/debugobjects.c:632 at __debug_check_no_obj_freed lib/debugobjects.c:1116 [inline], CPU#1: rcuc/1/28 > WARNING: lib/debugobjects.c:632 at debug_check_no_obj_freed+0x405/0x550 lib/debugobjects.c:1146, CPU#1: rcuc/1/28 > Modules linked in: > CPU: 1 UID: 0 PID: 28 Comm: rcuc/1 Tainted: G L syzkaller #0 PREEMPT_{RT,(full)} > Tainted: [L]=SOFTLOCKUP > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 > RIP: 0010:debug_print_object lib/debugobjects.c:629 [inline] > RIP: 0010:__debug_check_no_obj_freed lib/debugobjects.c:1116 [inline] > RIP: 0010:debug_check_no_obj_freed+0x44a/0x550 lib/debugobjects.c:1146 > Code: 89 44 24 20 e8 27 81 7f fd 48 8b 44 24 20 4c 8b 4d 00 4c 89 ef 48 c7 c6 a0 53 a7 8b 48 c7 c2 20 59 a7 8b 8b 0c 24 4d 89 f8 50 <67> 48 0f b9 3a 48 83 c4 08 4c 8b 6c 24 18 48 b9 00 00 00 00 00 fc > RSP: 0018:ffffc90000a2fa90 EFLAGS: 00010246 > RAX: ffffffff89f32240 RBX: ffffffff99a8edc0 RCX: 0000000000000000 > RDX: ffffffff8ba75920 RSI: ffffffff8ba753a0 RDI: ffffffff8f933740 > RBP: ffffffff8b4f5380 R08: ffff888033a47278 R09: ffffffff8b4f6700 > R10: dffffc0000000000 R11: ffffffff81b0c180 R12: ffff888033a47400 > R13: ffffffff8f933740 R14: ffff888033a47000 R15: ffff888033a47278 > FS: 0000000000000000(0000) GS:ffff888126279000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007fb873a4da08 CR3: 000000004cc78000 CR4: 00000000003526f0 > Call Trace: > > slab_free_hook mm/slub.c:2620 [inline] > slab_free mm/slub.c:6250 [inline] > kfree+0x13e/0x6c0 mm/slub.c:6565 > kobject_cleanup lib/kobject.c:689 [inline] > kobject_release lib/kobject.c:720 [inline] > kref_put include/linux/kref.h:65 [inline] > kobject_put+0x228/0x560 lib/kobject.c:737 > rcu_do_batch kernel/rcu/tree.c:2617 [inline] > rcu_core kernel/rcu/tree.c:2869 [inline] > rcu_cpu_kthread+0x99e/0x1470 kernel/rcu/tree.c:2957 > smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160 > kthread+0x388/0x470 kernel/kthread.c:436 > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 >