• Al Viro's avatar
    ecryptfs_lookup_interpose(): lower_dentry->d_parent is not stable either · 762c6968
    Al Viro authored
    We need to get the underlying dentry of parent; sure, absent the races
    it is the parent of underlying dentry, but there's nothing to prevent
    losing a timeslice to preemtion in the middle of evaluation of
    lower_dentry->d_parent->d_inode, having another process move lower_dentry
    around and have its (ex)parent not pinned anymore and freed on memory
    pressure.  Then we regain CPU and try to fetch ->d_inode from memory
    that is freed by that point.
    
    dentry->d_parent *is* stable here - it's an argument of ->lookup() and
    we are guaranteed that it won't be moved anywhere until we feed it
    to d_add/d_splice_alias.  So we safely go that way to get to its
    underlying dentry.
    
    Cc: stable@vger.kernel.org # since 2009 or so
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    762c6968
inode.c 32.2 KB