CVE-2025-38358: In the Linux kernel, the following vulnerability has been resolved:  btrfs: fix race between async reclaim worker and close_ctree()  Syzbot reported an assertion failure due to an attempt to add a delayed iput after we have set BTRFS_FS_STATE_NO_DELAYED_IPUT in the fs_info state:    WARNING: CPU: 0 PID: 65 at fs/btrfs/inode.c:3420 btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420   Modules linked in:   CPU: 0 UID: 0 PID: 65 Comm: kworker/u8:4 Not tainted 6.15.0-next-20250530-syzkaller #0 PREEMPT(full)   Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025   Workqueue: btrfs-endio-write btrfs_work_helper   RIP: 0010:btrfs_add_delayed_iput+0x2f8/0x370 fs/btrfs/inode.c:3420   Code: 4e ad 5d (...)   RSP: 0018:ffffc9000213f780 EFLAGS: 00010293   RAX: ffffffff83c635b7 RBX: ffff888058920000 RCX: ffff88801c769e00   RDX: 0000000000000000 RSI: 0000000000000100 RDI: 0000000000000000   RBP: 0000000000000001 R08: ffff888058921b67 R09: 1ffff1100b12436c   R10: dffffc0000000000 R11: ffffed100b12436d R12: 0000000000000001   R13: dffffc0000000000 R14: ffff88807d748000 R15: 0000000000000100   FS:  0000000000000000(0000) GS:ffff888125c53000(0000) knlGS:0000000000000000   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033   CR2: 00002000000bd038 CR3: 000000006a142000 CR4: 00000000003526f0   DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000   DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400   Call Trace:    <TASK>    btrfs_put_ordered_extent+0x19f/0x470 fs/btrfs/ordered-data.c:635    btrfs_finish_one_ordered+0x11d8/0x1b10 fs/btrfs/inode.c:3312    btrfs_work_helper+0x399/0xc20 fs/btrfs/async-thread.c:312    process_one_work kernel/workqueue.c:3238 [inline]    process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321    worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402    kthread+0x70e/0x8a0 kernel/kthread.c:464    ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148    ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245    </TASK>  This can happen due to a race with the async reclaim worker like this:  1) The async metadata reclaim worker enters shrink_delalloc(), which calls    btrfs_start_delalloc_roots() with an nr_pages argument that has a value    less than LONG_MAX, and that in turn enters start_delalloc_inodes(),    which sets the local variable 'full_flush' to false because    wbc->nr_to_write is less than LONG_MAX;  2) There it finds inode X in a root's delalloc list, grabs a reference for    inode X (with igrab()), and triggers writeback for it with    filemap_fdatawrite_wbc(), which creates an ordered extent for inode X;  3) The unmount sequence starts from another task, we enter close_ctree()    and we flush the workqueue fs_info->endio_write_workers, which waits    for the ordered extent for inode X to complete and when dropping the    last reference of the ordered extent, with btrfs_put_ordered_extent(),    when we call btrfs_add_delayed_iput() we don't add the inode to the    list of delayed iputs because it has a refcount of 2, so we decrement    it to 1 and return;  4) Shortly after at close_ctree() we call btrfs_run_delayed_iputs() which    runs all delayed iputs, and then we set BTRFS_FS_STATE_NO_DELAYED_IPUT    in the fs_info state;  5) The async reclaim worker, after calling filemap_fdatawrite_wbc(), now    calls btrfs_add_delayed_iput() for inode X and there we trigger an    assertion failure since the fs_info state has the flag    BTRFS_FS_STATE_NO_DELAYED_IPUT set.  Fix this by setting BTRFS_FS_STATE_NO_DELAYED_IPUT only after we wait for the async reclaim workers to finish, after we call cancel_work_sync() for them at close_ctree(), and by running delayed iputs after wait for the reclaim workers to finish and before setting the bit.  This race was recently introduced by commit 19e60b2a95f5 ("btrfs: add extra warning if delayed iput is added when it's not allowed"). Without the new validation at btrfs_add_delayed_iput(),  ---truncated---