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List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6e02:1a6c:b0:3d0:4c9c:965f with SMTP id e9e14a558f8ab-3d7ec2732fdmr3494205ab.20.1744317209752; Thu, 10 Apr 2025 13:33:29 -0700 (PDT) Date: Thu, 10 Apr 2025 13:33:29 -0700 In-Reply-To: <67eba499.050a0220.297a31.0009.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <67f82b19.050a0220.355867.000f.GAE@google.com> Subject: Re: [syzbot] [kernfs?] possible deadlock in kernfs_iop_getattr From: syzbot To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tj@kernel.org Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: 2eb959eeecc6 Merge tag 'for-linus-6.15a-rc2-tag' of git://.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=16fdf23f980000 kernel config: https://syzkaller.appspot.com/x/.config?x=4c918722cb7e3d7 dashboard link: https://syzkaller.appspot.com/bug?extid=4bb2305559463e8f6a2a compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1352b7e4580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17499d78580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-2eb959ee.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/e48cee99a6e9/vmlinux-2eb959ee.xz kernel image: https://storage.googleapis.com/syzbot-assets/6087fbb17208/bzImage-2eb959ee.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+4bb2305559463e8f6a2a@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected 6.15.0-rc1-syzkaller-00095-g2eb959eeecc6 #0 Not tainted ------------------------------------------------------ syz-executor105/5947 is trying to acquire lock: ffff88801c68e9e0 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_getattr+0x9c/0xf0 fs/kernfs/inode.c:191 but task is already holding lock: ffff8881070c75a8 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:215 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&q->q_usage_counter(io)#26){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x179/0x290 block/blk-mq.c:4348 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4395 loop_add+0x496/0xb70 drivers/block/loop.c:2067 loop_init+0x164/0x270 drivers/block/loop.c:2302 do_one_initcall+0x120/0x6e0 init/main.c:1257 do_initcall_level init/main.c:1319 [inline] do_initcalls init/main.c:1335 [inline] do_basic_setup init/main.c:1354 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1567 kernel_init+0x1c/0x2b0 init/main.c:1457 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4028 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4042 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4102 [inline] slab_alloc_node mm/slub.c:4180 [inline] kmem_cache_alloc_noprof+0x53/0x3b0 mm/slub.c:4207 __kernfs_iattrs+0xbc/0x3f0 fs/kernfs/inode.c:37 kernfs_iattrs fs/kernfs/inode.c:60 [inline] __kernfs_setattr+0x4d/0x3c0 fs/kernfs/inode.c:73 kernfs_iop_setattr+0xda/0x120 fs/kernfs/inode.c:127 notify_change+0x6a6/0x1230 fs/attr.c:552 do_truncate+0x15b/0x220 fs/open.c:65 handle_truncate fs/namei.c:3466 [inline] do_open fs/namei.c:3849 [inline] path_openat+0x2761/0x2d40 fs/namei.c:4004 do_filp_open+0x20b/0x470 fs/namei.c:4031 do_sys_openat2+0x11b/0x1d0 fs/open.c:1429 do_sys_open fs/open.c:1444 [inline] __do_sys_openat fs/open.c:1460 [inline] __se_sys_openat fs/open.c:1455 [inline] __x64_sys_openat+0x174/0x210 fs/open.c:1455 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (iattr_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746 __kernfs_iattrs+0x2b/0x3f0 fs/kernfs/inode.c:32 kernfs_iattrs fs/kernfs/inode.c:60 [inline] __kernfs_setattr+0x4d/0x3c0 fs/kernfs/inode.c:73 kernfs_iop_setattr+0xda/0x120 fs/kernfs/inode.c:127 notify_change+0x6a6/0x1230 fs/attr.c:552 do_truncate+0x15b/0x220 fs/open.c:65 handle_truncate fs/namei.c:3466 [inline] do_open fs/namei.c:3849 [inline] path_openat+0x2761/0x2d40 fs/namei.c:4004 do_filp_open+0x20b/0x470 fs/namei.c:4031 do_sys_openat2+0x11b/0x1d0 fs/open.c:1429 do_sys_open fs/open.c:1444 [inline] __do_sys_openat fs/open.c:1460 [inline] __se_sys_openat fs/open.c:1455 [inline] __x64_sys_openat+0x174/0x210 fs/open.c:1455 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&root->kernfs_iattr_rwsem){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain kernel/locking/lockdep.c:3909 [inline] __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235 lock_acquire kernel/locking/lockdep.c:5866 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823 down_read+0x9b/0x480 kernel/locking/rwsem.c:1524 kernfs_iop_getattr+0x9c/0xf0 fs/kernfs/inode.c:191 vfs_getattr_nosec+0x29a/0x3a0 fs/stat.c:208 vfs_getattr+0x4a/0x60 fs/stat.c:246 loop_query_min_dio_size.isra.0+0x120/0x260 drivers/block/loop.c:529 loop_assign_backing_file drivers/block/loop.c:582 [inline] loop_change_fd drivers/block/loop.c:645 [inline] lo_ioctl+0x1ce0/0x26d0 drivers/block/loop.c:1569 blkdev_ioctl+0x274/0x6d0 block/ioctl.c:698 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl fs/ioctl.c:892 [inline] __x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &root->kernfs_iattr_rwsem --> fs_reclaim --> &q->q_usage_counter(io)#26 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#26); lock(fs_reclaim); lock(&q->q_usage_counter(io)#26); rlock(&root->kernfs_iattr_rwsem); *** DEADLOCK *** 3 locks held by syz-executor105/5947: #0: ffff8880259ff368 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable drivers/block/loop.c:118 [inline] #0: ffff8880259ff368 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_change_fd drivers/block/loop.c:610 [inline] #0: ffff8880259ff368 (&lo->lo_mutex){+.+.}-{4:4}, at: lo_ioctl+0x2a9/0x26d0 drivers/block/loop.c:1569 #1: ffff8881070c75a8 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:215 #2: ffff8881070c75e0 (&q->q_usage_counter(queue)#20){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:215 stack backtrace: CPU: 2 UID: 0 PID: 5947 Comm: syz-executor105 Not tainted 6.15.0-rc1-syzkaller-00095-g2eb959eeecc6 #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2079 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2211 check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain kernel/locking/lockdep.c:3909 [inline] __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235 lock_acquire kernel/locking/lockdep.c:5866 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823 down_read+0x9b/0x480 kernel/locking/rwsem.c:1524 kernfs_iop_getattr+0x9c/0xf0 fs/kernfs/inode.c:191 vfs_getattr_nosec+0x29a/0x3a0 fs/stat.c:208 vfs_getattr+0x4a/0x60 fs/stat.c:246 loop_query_min_dio_size.isra.0+0x120/0x260 drivers/block/loop.c:529 loop_assign_backing_file drivers/block/loop.c:582 [inline] loop_change_fd drivers/block/loop.c:645 [inline] lo_ioctl+0x1ce0/0x26d0 drivers/block/loop.c:1569 blkdev_ioctl+0x274/0x6d0 block/ioctl.c:698 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl fs/ioctl.c:892 [inline] __x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f787e0f8e29 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 18 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffd0efe9d88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f787e0f8e29 RDX: 0000000000000005 RSI: 0000000000004c06 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f787e142036 R13: 00007ffd0efe9dc0 R14: 00007ffd0efe9e00 R15: 0000000000000000 --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.