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* [syzbot] [btrfs?] possible deadlock in btrfs_search_slot (2)
@ 2023-08-25 19:50 syzbot
  0 siblings, 0 replies; only message in thread
From: syzbot @ 2023-08-25 19:50 UTC (permalink / raw)
  To: clm, dsterba, josef, linux-btrfs, linux-fsdevel, linux-kernel,
	syzkaller-bugs

Hello,

syzbot found the following issue on:

HEAD commit:    f7757129e3de Merge tag 'v6.5-p3' of git://git.kernel.org/p..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16f597efa80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1b32f62c755c3a9c
dashboard link: https://syzkaller.appspot.com/bug?extid=bf66ad948981797d2f1d
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f91660680000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17b3a25ba80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e974b38a90bd/disk-f7757129.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fdc5c90820c9/vmlinux-f7757129.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b21384bf7402/bzImage-f7757129.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/404dc73f5fcc/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bf66ad948981797d2f1d@syzkaller.appspotmail.com

BTRFS info (device loop0): enabling ssd optimizations
BTRFS info (device loop0): using spread ssd allocation scheme
BTRFS info (device loop0): turning on sync discard
BTRFS info (device loop0): using free space tree
======================================================
WARNING: possible circular locking dependency detected
6.5.0-rc7-syzkaller-00004-gf7757129e3de #0 Not tainted
------------------------------------------------------
syz-executor277/5012 is trying to acquire lock:
ffff88802df41710 (btrfs-tree-01){++++}-{3:3}, at: __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136

but task is already holding lock:
ffff88802df418e8 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (btrfs-tree-00){++++}-{3:3}:
       down_read_nested+0x49/0x2f0 kernel/locking/rwsem.c:1645
       __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136
       btrfs_search_slot+0x13a4/0x2f80 fs/btrfs/ctree.c:2302
       btrfs_init_root_free_objectid+0x148/0x320 fs/btrfs/disk-io.c:4955
       btrfs_init_fs_root fs/btrfs/disk-io.c:1128 [inline]
       btrfs_get_root_ref+0x5ae/0xae0 fs/btrfs/disk-io.c:1338
       btrfs_get_fs_root fs/btrfs/disk-io.c:1390 [inline]
       open_ctree+0x29c8/0x3030 fs/btrfs/disk-io.c:3494
       btrfs_fill_super+0x1c7/0x2f0 fs/btrfs/super.c:1154
       btrfs_mount_root+0x7e0/0x910 fs/btrfs/super.c:1519
       legacy_get_tree+0xef/0x190 fs/fs_context.c:611
       vfs_get_tree+0x8c/0x270 fs/super.c:1519
       fc_mount fs/namespace.c:1112 [inline]
       vfs_kern_mount+0xbc/0x150 fs/namespace.c:1142
       btrfs_mount+0x39f/0xb50 fs/btrfs/super.c:1579
       legacy_get_tree+0xef/0x190 fs/fs_context.c:611
       vfs_get_tree+0x8c/0x270 fs/super.c:1519
       do_new_mount+0x28f/0xae0 fs/namespace.c:3335
       do_mount fs/namespace.c:3675 [inline]
       __do_sys_mount fs/namespace.c:3884 [inline]
       __se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3861
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (btrfs-tree-01){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3142 [inline]
       check_prevs_add kernel/locking/lockdep.c:3261 [inline]
       validate_chain kernel/locking/lockdep.c:3876 [inline]
       __lock_acquire+0x39ff/0x7f70 kernel/locking/lockdep.c:5144
       lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5761
       down_read_nested+0x49/0x2f0 kernel/locking/rwsem.c:1645
       __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136
       btrfs_tree_read_lock fs/btrfs/locking.c:142 [inline]
       btrfs_read_lock_root_node+0x292/0x3c0 fs/btrfs/locking.c:281
       btrfs_search_slot_get_root fs/btrfs/ctree.c:1832 [inline]
       btrfs_search_slot+0x4ff/0x2f80 fs/btrfs/ctree.c:2154
       btrfs_lookup_inode+0xdc/0x480 fs/btrfs/inode-item.c:412
       btrfs_read_locked_inode fs/btrfs/inode.c:3892 [inline]
       btrfs_iget_path+0x2d9/0x1520 fs/btrfs/inode.c:5716
       btrfs_search_path_in_tree_user fs/btrfs/ioctl.c:1961 [inline]
       btrfs_ioctl_ino_lookup_user+0x77a/0xf50 fs/btrfs/ioctl.c:2105
       btrfs_ioctl+0xb0b/0xd40 fs/btrfs/ioctl.c:4683
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(btrfs-tree-00);
                               lock(btrfs-tree-01);
                               lock(btrfs-tree-00);
  rlock(btrfs-tree-01);

 *** DEADLOCK ***

1 lock held by syz-executor277/5012:
 #0: ffff88802df418e8 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136

stack backtrace:
CPU: 1 PID: 5012 Comm: syz-executor277 Not tainted 6.5.0-rc7-syzkaller-00004-gf7757129e3de #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 check_noncircular+0x375/0x4a0 kernel/locking/lockdep.c:2195
 check_prev_add kernel/locking/lockdep.c:3142 [inline]
 check_prevs_add kernel/locking/lockdep.c:3261 [inline]
 validate_chain kernel/locking/lockdep.c:3876 [inline]
 __lock_acquire+0x39ff/0x7f70 kernel/locking/lockdep.c:5144
 lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5761
 down_read_nested+0x49/0x2f0 kernel/locking/rwsem.c:1645
 __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136
 btrfs_tree_read_lock fs/btrfs/locking.c:142 [inline]
 btrfs_read_lock_root_node+0x292/0x3c0 fs/btrfs/locking.c:281
 btrfs_search_slot_get_root fs/btrfs/ctree.c:1832 [inline]
 btrfs_search_slot+0x4ff/0x2f80 fs/btrfs/ctree.c:2154
 btrfs_lookup_inode+0xdc/0x480 fs/btrfs/inode-item.c:412
 btrfs_read_locked_inode fs/btrfs/inode.c:3892 [inline]
 btrfs_iget_path+0x2d9/0x1520 fs/btrfs/inode.c:5716
 btrfs_search_path_in_tree_user fs/btrfs/ioctl.c:1961 [inline]
 btrfs_ioctl_ino_lookup_user+0x77a/0xf50 fs/btrfs/ioctl.c:2105
 btrfs_ioctl+0xb0b/0xd40 fs/btrfs/ioctl.c:4683
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f0bec94ea39
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 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:00007ffcde5751e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffcde5753b8 RCX: 00007f0bec94ea39
RDX: 0000000020000040 RSI: 00000000d000943e RDI: 0000000000000004
RBP: 00007f0bec9c6610 R08:


---
This report is generated by a bot. It may contain errors.
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If the bug is already fixed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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If you want to overwrite bug's subsystems, reply with:
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(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

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2023-08-25 19:50 [syzbot] [btrfs?] possible deadlock in btrfs_search_slot (2) syzbot

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