sf_unlink_aux: potential null pointer dereference on dentry

[ColinIanKing]

Function sf_unlink_aux() in vboxsf/dirops.c performs a dereference on dentry with the following call:

    err = sf_path_from_dentry(__func__, sf_g, sf_i, dentry, &path);

However, a few statements later dentry is being checked to see if it is a NULL pointer:

    if (   dentry
        && dentry->d_inode
        && ((dentry->d_inode->i_mode & S_IFLNK) == S_IFLNK))
        fFlags |= SHFL_REMOVE_SYMLINK;

Either that null pointer check is redundant or it dentry really could be NULL, in which case the earlier call to sf_path_from_dentry with a null dentry can trip a null pointer deference bug on dentry.

Anyhow, the current code looks suspect and should be fixed.

[Frank Mehnert]

denry is never NULL. The check is superfluous. Fixed the code but it's not necessary to open tickets for such trivial issues.