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List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [btrfs?] possible deadlock in btrfs_read_chunk_tree To: syzbot , clm@fb.com, dsterba@suse.com, josef@toxicpanda.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, wqu@suse.com References: <685aa401.050a0220.2303ee.0009.GAE@google.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1YAUJEP5a 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jLP+JxHiIZIe0mJym5EtBv3TA65uVsFNE32iUOb2k2NyBwQfGda8YpSxL7hEHh2Pi1wgCxJTW cIWcgvhZXE7kYdYrT5S/jKAone7+a6JK3PugjxvRe5z3OKbNBg8dljhhoK1MqcTgMFsywDwBp mepGDtHq3+2tk/Fvu5Vj/MrteW7ymZHs5rNCrLa+UU2/I6dd3erdJDqmeBe5OG0uqjQMLVDOv saijaB6cU4hOasbWULbpg6gmcaqAdmM6bOOojY/H/pU23aCiR434YD3ilFjxssZMbF4km+57y iMuMbdFpfzPcsrn7iBmThDrxqPScSGfNeQjsZAooKzTZ3i37+YcOSQNQ+ONgFoEXmOzWqqOOJ 5lQyA0Jqi1FKIscflHPlh+rsy+4NIOlqWjuVvtqwUZRircd9uJ+a9XfIWl6x/mPED5uSORSrT F7pNhbEi97Q== #syz test: https://github.com/adam900710/linux.git shutdown =E5=9C=A8 2025/6/24 22:41, syzbot =E5=86=99=E9=81=93: > Hello, >=20 > syzbot found the following issue on: >=20 > HEAD commit: 5d4809e25903 Add linux-next specific files for 20250620 > git tree: linux-next > console+strace: https://syzkaller.appspot.com/x/log.txt?x=3D1421b3705800= 00 > kernel config: https://syzkaller.appspot.com/x/.config?x=3D58afc4b78b52= b7e3 > dashboard link: https://syzkaller.appspot.com/bug?extid=3Dfa90fcaa28f5cd= 4b1fc1 > compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e077= 57-1~exp1~20250514183223.118), Debian LLD 20.1.6 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=3D11f1cb0c58= 0000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=3D14aff30c5800= 00 >=20 > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/16492bf6b788/di= sk-5d4809e2.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/7be284ded1de/vmlin= ux-5d4809e2.xz > kernel image: https://storage.googleapis.com/syzbot-assets/467d717f0d9c/= bzImage-5d4809e2.xz > mounted in repro: https://storage.googleapis.com/syzbot-assets/4a74fbfa0= b0f/mount_0.gz > fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=3D10= 30cdd4580000) >=20 > The issue was bisected to: >=20 > commit 7aacdf6feed1ca882339ebd3895a233373b40a1e > Author: Qu Wenruo > Date: Tue Jun 17 05:19:38 2025 +0000 >=20 > btrfs: delay btrfs_open_devices() until super block is created >=20 > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=3D14d29b0c5= 80000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=3D16d29b0c5= 80000 > console output: https://syzkaller.appspot.com/x/log.txt?x=3D12d29b0c5800= 00 >=20 > IMPORTANT: if you fix the issue, please add the following tag to the com= mit: > Reported-by: syzbot+fa90fcaa28f5cd4b1fc1@syzkaller.appspotmail.com > Fixes: 7aacdf6feed1 ("btrfs: delay btrfs_open_devices() until super bloc= k is created") >=20 > BTRFS info (device loop0): using sha256 (sha256-x86_64) checksum algorit= hm > BTRFS info (device loop0): disk space caching is enabled > BTRFS warning (device loop0): space cache v1 is being deprecated and wil= l be removed in a future release, please use -o space_cache=3Dv2 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D > WARNING: possible circular locking dependency detected > 6.16.0-rc2-next-20250620-syzkaller #0 Not tainted > ------------------------------------------------------ > syz-executor123/5843 is trying to acquire lock: > ffffffff8e6e9fe8 (uuid_mutex){+.+.}-{4:4}, at: btrfs_read_chunk_tree+0xe= f/0x2170 fs/btrfs/volumes.c:7462 >=20 > but task is already holding lock: > ffff8880328ea0e0 (&type->s_umount_key#41/1){+.+.}-{4:4}, at: alloc_super= +0x204/0x970 fs/super.c:345 >=20 > which lock already depends on the new lock. >=20 >=20 > the existing dependency chain (in reverse order) is: >=20 > -> #1 (&type->s_umount_key#41/1){+.+.}-{4:4}: > lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 > down_write_nested+0x9d/0x200 kernel/locking/rwsem.c:1693 > alloc_super+0x204/0x970 fs/super.c:345 > sget_fc+0x329/0xa40 fs/super.c:761 > btrfs_get_tree_super fs/btrfs/super.c:1867 [inline] > btrfs_get_tree_subvol fs/btrfs/super.c:2059 [inline] > btrfs_get_tree+0x4c6/0x12d0 fs/btrfs/super.c:2093 > vfs_get_tree+0x8f/0x2b0 fs/super.c:1804 > do_new_mount+0x24a/0xa40 fs/namespace.c:3902 > do_mount fs/namespace.c:4239 [inline] > __do_sys_mount fs/namespace.c:4450 [inline] > __se_sys_mount+0x317/0x410 fs/namespace.c:4427 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f >=20 > -> #0 (uuid_mutex){+.+.}-{4:4}: > check_prev_add kernel/locking/lockdep.c:3168 [inline] > check_prevs_add kernel/locking/lockdep.c:3287 [inline] > validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911 > __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 > lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 > __mutex_lock_common kernel/locking/mutex.c:602 [inline] > __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747 > btrfs_read_chunk_tree+0xef/0x2170 fs/btrfs/volumes.c:7462 > open_ctree+0x17f2/0x3a10 fs/btrfs/disk-io.c:3458 > btrfs_fill_super fs/btrfs/super.c:984 [inline] > btrfs_get_tree_super fs/btrfs/super.c:1922 [inline] > btrfs_get_tree_subvol fs/btrfs/super.c:2059 [inline] > btrfs_get_tree+0xc6f/0x12d0 fs/btrfs/super.c:2093 > vfs_get_tree+0x8f/0x2b0 fs/super.c:1804 > do_new_mount+0x24a/0xa40 fs/namespace.c:3902 > do_mount fs/namespace.c:4239 [inline] > __do_sys_mount fs/namespace.c:4450 [inline] > __se_sys_mount+0x317/0x410 fs/namespace.c:4427 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f >=20 > other info that might help us debug this: >=20 > Possible unsafe locking scenario: >=20 > CPU0 CPU1 > ---- ---- > lock(&type->s_umount_key#41/1); > lock(uuid_mutex); > lock(&type->s_umount_key#41/1); > lock(uuid_mutex); >=20 > *** DEADLOCK *** >=20 > 1 lock held by syz-executor123/5843: > #0: ffff8880328ea0e0 (&type->s_umount_key#41/1){+.+.}-{4:4}, at: alloc= _super+0x204/0x970 fs/super.c:345 >=20 > stack backtrace: > CPU: 1 UID: 0 PID: 5843 Comm: syz-executor123 Not tainted 6.16.0-rc2-nex= t-20250620-syzkaller #0 PREEMPT(full) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS = Google 05/07/2025 > Call Trace: > > dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 > print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046 > check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178 > check_prev_add kernel/locking/lockdep.c:3168 [inline] > check_prevs_add kernel/locking/lockdep.c:3287 [inline] > validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911 > __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 > lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 > __mutex_lock_common kernel/locking/mutex.c:602 [inline] > __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747 > btrfs_read_chunk_tree+0xef/0x2170 fs/btrfs/volumes.c:7462 > open_ctree+0x17f2/0x3a10 fs/btrfs/disk-io.c:3458 > btrfs_fill_super fs/btrfs/super.c:984 [inline] > btrfs_get_tree_super fs/btrfs/super.c:1922 [inline] > btrfs_get_tree_subvol fs/btrfs/super.c:2059 [inline] > btrfs_get_tree+0xc6f/0x12d0 fs/btrfs/super.c:2093 > vfs_get_tree+0x8f/0x2b0 fs/super.c:1804 > do_new_mount+0x24a/0xa40 fs/namespace.c:3902 > do_mount fs/namespace.c:4239 [inline] > __do_sys_mount fs/namespace.c:4450 [inline] > __se_sys_mount+0x317/0x410 fs/namespace.c:4427 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7fda63124f3a > Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 00 00 66 2e 0f 1f = 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007ffd76f19cb8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5 > RAX: ffffffffffffffda RBX: 00007ffd76f19cd0 RCX: 00007fda63124f3a > RDX: 00002000000004c0 RSI: 00002000000015c0 RDI: 00007ffd76f19cd0 > RBP: 00002000000004c0 R08: 00007ffd76f19d10 R09: 0000000000005598 > R10: 0000000002000000 R11: 0000000000000282 R12: 00002000000015c0 > R13: 00007ffd76f19d10 R14: 0000000000000003 R15: 0000000002000000 > > BTRFS info (device loop0): rebuilding free space tree > BTRFS info (device loop0): disabling free space tree > BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPAC= E_TREE (0x1) > BTRFS info (device loop0): clearing compat-ro feature flag for FREE_SPAC= E_TREE_VALID (0x2) >=20 >=20 > --- > 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. >=20 > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > For information about bisection process see: https://goo.gl/tpsmEJ#bisec= tion >=20 > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title >=20 > 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. >=20 > 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) >=20 > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report >=20 > If you want to undo deduplication, reply with: > #syz undup >=20