• Christian Borntraeger's avatar
    anon_inodes: use fops->owner for module refcount · e3a2a0d4
    Christian Borntraeger authored
    There is an imbalance for anonymous inodes. If the fops->owner field is set,
    the module reference count of owner is decreases on release.
    ("filp_close" --> "__fput" ---> "fops_put")
    On the other hand, anon_inode_getfd does not increase the module reference
    count of owner. This causes two problems:
    - if owner is set, the module refcount goes negative
    - if owner is not set, the module can be unloaded while code is running
    This patch changes anon_inode_getfd to be symmetric regarding fops->owner
    I have checked all existing users of anon_inode_getfd. Noone sets fops->owner,
    thats why nobody has seen the module refcount negative. The refcounting was
    tested with a patched and unpatched KVM module.(see patch 2/2) I also did an
    epoll_open/close test.
    Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
    Reviewed-by: default avatarDavide Libenzi <davidel@xmailserver.org>
    Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
anon_inodes.c 5.05 KB