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    SubjectRe: [PATCH] loop: fput() called in loop_clr_fd() may cause bd_mutex recursive locking
    On Sun, Dec 18, 2011 at 01:19:28AM +0300, Sergey Senozhatsky wrote:

    > Sorry, why is that a false positive?
    > blkdev_put() calls lo_release() while holding bd_mutex,
    > lo_release() calls loop_clr_fd() -> fput(). fput() once again
    > attempts to grub already held bd_mutex calling blkdev_put().
    > Looks like a recursion to me.

    Because of this:
    /* Avoid recursion */
    f = file;
    while (is_loop_device(f)) {
    struct loop_device *l;

    if (f->f_mapping->host->i_bdev == bdev)
    goto out_putf;

    l = f->f_mapping->host->i_bdev->bd_disk->private_data;
    if (l->lo_state == Lo_unbound) {
    error = -EINVAL;
    goto out_putf;
    f = l->lo_backing_file;
    in loop_set_fd(). Think of it for a minute - if we could run into the
    same bdev in that recursion, what would have happened on read() from
    that sucker? So yes, it is a false positive. And your patch would
    simply leave the underlying device opened, with all the consequences...

     \ /
      Last update: 2011-12-17 23:33    [W:0.038 / U:121.468 seconds]
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