btrfs: release path before inode lookup during the ino lookup ioctl

In the Linux kernel, the following vulnerability has been resolved:

btrfs: release path before inode lookup during the ino lookup ioctl

During the ino lookup ioctl we can end up calling btrfs_iget() to get an

inode reference while we are holding on a root's btree. If btrfs_iget()

needs to lookup the inode from the root's btree, because it's not

currently loaded in memory, then it will need to lock another or the

same path in the same root btree. This may result in a deadlock and

trigger the following lockdep splat:

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

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