From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f198.google.com (mail-oi1-f198.google.com [209.85.167.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 92A55214A84 for ; Sat, 3 Oct 2026 02:36:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790994992; cv=none; b=rqHHQ2gBe7D5CS2Z3/8Q1FLI+fdyPKsqGFf65G5Qaj/Eg53HfAoJSGaKY0qUBy4PHLIDuK4ZduupEuc/OvQQxYLlkd/PPxOvpXgkuIKSD2iQvPtcPzkE9ZFABQsla4j8wgXJ/6f2j5+/rVnPYTSqdp4a/fnaP6FsHiS+9TKAha0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790994992; c=relaxed/simple; bh=KNcbqMrALl7aMYhgsSOtyeru+oiGxpGaO1VMbrUQ5KE=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=eye56Q9EVzjdcy6e6lNm2c9fx1UNEVV315wOujrtV3S75G4LZs98132MaTRWfOxI34MzAciKtCbogyUYvcvnNlsolVt0Ty4qNTQ6C7sU1KYRgY14rec0R6k+Mj3/MySBWleQ/mZmmcpgQ0uWRevEejZrohCurgCaWUpbmgzkLvo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.167.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oi1-f198.google.com with SMTP id 5614622812f47-4dab94dc3e7so209993b6e.0 for ; Fri, 02 Oct 2026 19:36:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790994989; x=1791599789; h=content-type:to:from:subject:message-id:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=ACQlxslOuzPIbXuewMrLTvlOAlThRUPxLWuXinhH048=; b=MMWCdoyu9qgeFvMu4kFcCr/2Y2hQx8x9ztg11A9Zwzr+TVi3oODL5/p3rxP66A2AIE 5acOFsHPuKaV6TjpqrXi4rBV/Hr0hqMGaybSQ1QQ8A1+ZqOkx6kMjRlg9qU8pKaXTjZW IU4nifR+xtdew9ridRfysLiL5F9D5kT2wvmpCkJkoxE7c6G2JHL+naPqPcae1XUIDbE3 d/vAnzvIzXoFUTFlpphil04L5PdoKUAPKzNUikHpZm1PhAiVOPyFYNHGbGwlYV0k8mDQ SCmevETFftuNJJ/NW45liek6GEC2veQq4AiesgyaPMAmhuvSUf2KrBzlucf8HwmN94eg +Aog== X-Gm-Message-State: AFuF++kYdB4QUu+am6ldpSdpecF29QfAguqsbAoIuWs7UoM92fxP1Rvq 9aYxb+rooT9eViBAhe0UrY5LBH75Hwzp1/uhhN8zJOqKi0NjYNKCDN5QG91j3hhzbq42mTSCnzg svwbATq0UJs7Tfi5d+gw6wAvk8Vnds4i6mzcJ3931AdP/Ri2KmwOrtG41RZI= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:3502:b0:4d5:27da:a492 with SMTP id 5614622812f47-4f67b0245d8mr1382262b6e.44.1790994989393; Fri, 02 Oct 2026 19:36:29 -0700 (PDT) Date: Fri, 02 Oct 2026 19:36:29 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ac06a2d.34119e79.2f92f3.000d.GAE@google.com> Subject: [syzbot] [kernel?] possible deadlock in mtrr_del_page From: syzbot To: linux-kernel@vger.kernel.org, peterz@infradead.org, syzkaller-bugs@googlegroups.com, tglx@kernel.org Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 72d3fcf802c4 Linux 7.3-rc5 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10d8ae05580000 kernel config: https://syzkaller.appspot.com/x/.config?x=9d4242cb1c54cdf7 dashboard link: https://syzkaller.appspot.com/bug?extid=342762971f666337474e compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/dc3ad46af4b1/disk-72d3fcf8.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/622cf26726fb/vmlinux-72d3fcf8.xz kernel image: https://storage.googleapis.com/syzbot-assets/07dc9df89174/bzImage-72d3fcf8.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+342762971f666337474e@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.9.5848/21744 is trying to acquire lock: ffffffff8eba04e0 (mtrr_mutex){+.+.}-{4:4}, at: mtrr_del_page+0xf1/0x560 arch/x86/kernel/cpu/mtrr/mtrr.c:408 but task is already holding lock: ffffffff8ebe9970 (cpu_hotplug_lock){++++}-{0:0}, at: mtrr_del_page+0xe3/0x560 arch/x86/kernel/cpu/mtrr/mtrr.c:407 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #7 (cpu_hotplug_lock){++++}-{0:0}: percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read include/linux/percpu-rwsem.h:77 [inline] cpus_read_lock+0x42/0x160 kernel/cpu.c:490 static_key_slow_inc+0x12/0x30 kernel/jump_label.c:190 nbd_genl_reconnect_sock_cb+0x69a/0xbb0 drivers/block/nbd.c:1377 nbd_genl_foreach_sock+0x265/0x450 drivers/block/nbd.c:2152 nbd_genl_reconfigure+0xbbb/0x1040 drivers/block/nbd.c:2477 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2575 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1338 [inline] netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1364 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1919 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800 __sock_sendmsg net/socket.c:815 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2713 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767 __sys_sendmsg net/socket.c:2799 [inline] __do_sys_sendmsg net/socket.c:2804 [inline] __se_sys_sendmsg net/socket.c:2802 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #6 (&nsock->tx_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x373/0xff0 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560 kthread+0x38b/0x480 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 -> #5 (&cmd->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 nbd_queue_rq+0xc1/0xff0 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x16c/0x300 block/blk-mq.c:2532 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560 kthread+0x38b/0x480 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 -> #4 (set->srcu){.+.+}-{0:0}: srcu_lock_sync include/linux/srcu.h:210 [inline] __synchronize_srcu+0xc9/0x2f0 kernel/rcu/srcutree.c:1462 elevator_switch+0x1e8/0x7b0 block/elevator.c:576 elevator_change+0x2fa/0x480 block/elevator.c:681 elevator_set_default+0x375/0x440 block/elevator.c:754 blk_register_queue+0x3f3/0x4e0 block/blk-sysfs.c:992 __add_disk+0x6b8/0xdb0 block/genhd.c:531 add_disk_fwnode+0x100/0x3a0 block/genhd.c:600 add_disk include/linux/blkdev.h:798 [inline] nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:2026 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743 do_one_initcall+0x250/0x870 init/main.c:1362 do_initcall_level+0x10a/0x1a0 init/main.c:1424 do_initcalls+0x59/0xa0 init/main.c:1440 kernel_init_freeable+0x29d/0x3e0 init/main.c:1675 kernel_init+0x22/0x1d0 init/main.c:1565 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #3 (&q->elevator_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 queue_requests_store+0x45b/0x5f0 block/blk-sysfs.c:124 queue_attr_store+0x207/0x2b0 block/blk-sysfs.c:906 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x612/0xba0 fs/read_write.c:687 ksys_write+0x150/0x270 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (&q->q_usage_counter(io)#66){++++}-{0:0}: blk_alloc_queue+0x544/0x690 block/blk-core.c:504 blk_mq_alloc_queue block/blk-mq.c:4420 [inline] __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4467 null_add_dev+0xe82/0x1d70 drivers/block/null_blk/main.c:2017 null_create_dev drivers/block/null_blk/main.c:2114 [inline] null_init+0x1e3/0x390 drivers/block/null_blk/main.c:2178 do_one_initcall+0x250/0x870 init/main.c:1362 do_initcall_level+0x10a/0x1a0 init/main.c:1424 do_initcalls+0x59/0xa0 init/main.c:1440 kernel_init_freeable+0x29d/0x3e0 init/main.c:1675 kernel_init+0x22/0x1d0 init/main.c:1565 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4375 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4389 might_alloc include/linux/sched/mm.h:316 [inline] slab_pre_alloc_hook mm/slub.c:4636 [inline] slab_alloc_node mm/slub.c:4974 [inline] __do_kmalloc_node mm/slub.c:5413 [inline] __kmalloc_noprof+0xbc/0x720 mm/slub.c:5439 _kmalloc_noprof include/linux/slab.h:995 [inline] _kzalloc_noprof include/linux/slab.h:1312 [inline] mtrr_copy_map+0x71/0x140 arch/x86/kernel/cpu/mtrr/generic.c:413 mtrr_init_finalize+0x9/0x70 arch/x86/kernel/cpu/mtrr/mtrr.c:618 do_one_initcall+0x250/0x870 init/main.c:1362 do_initcall_level+0x10a/0x1a0 init/main.c:1424 do_initcalls+0x59/0xa0 init/main.c:1440 kernel_init_freeable+0x29d/0x3e0 init/main.c:1675 kernel_init+0x22/0x1d0 init/main.c:1565 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (mtrr_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 mtrr_del_page+0xf1/0x560 arch/x86/kernel/cpu/mtrr/mtrr.c:408 mtrr_ioctl+0xcb8/0x13b0 arch/x86/kernel/cpu/mtrr/if.c:244 pde_ioctl fs/proc/inode.c:374 [inline] proc_reg_unlocked_ioctl+0x1d6/0x2c0 fs/proc/inode.c:386 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: mtrr_mutex --> &nsock->tx_lock --> cpu_hotplug_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(cpu_hotplug_lock); lock(&nsock->tx_lock); lock(cpu_hotplug_lock); lock(mtrr_mutex); *** DEADLOCK *** locks held by syz.9.5848/21744: 1, last CPU#0: #0: ffffffff8ebe9970 (cpu_hotplug_lock){++++}-{0:0}, at: mtrr_del_page+0xe3/0x560 arch/x86/kernel/cpu/mtrr/mtrr.c:407 stack backtrace: CPU: 0 UID: 0 PID: 21744 Comm: syz.9.5848 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219 check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 mtrr_del_page+0xf1/0x560 arch/x86/kernel/cpu/mtrr/mtrr.c:408 mtrr_ioctl+0xcb8/0x13b0 arch/x86/kernel/cpu/mtrr/if.c:244 pde_ioctl fs/proc/inode.c:374 [inline] proc_reg_unlocked_ioctl+0x1d6/0x2c0 fs/proc/inode.c:386 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f30e659e159 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f30e73e8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f30e6825fa0 RCX: 00007f30e659e159 RDX: 0000200000000340 RSI: 00000000400c4d04 RDI: 0000000000000003 RBP: 00007f30e663506b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f30e6826038 R14: 00007f30e6825fa0 R15: 00007ffc80c63678 MTRR 1 not used --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup