ask-password: prevent buffer overrow when reading from keyring
    
    When we read from keyring, a temporary buffer is allocated in order to
    determine the size needed for the entire data. However, when zeroing that area,
    we use the data size returned by the read instead of the lesser size allocate
    for the buffer.
    
    That will cause memory corruption that causes systemd-cryptsetup to crash
    either when a single large password is used or when multiple passwords have
    already been pushed to the keyring.
    
    Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
    (cherry picked from commit 59c55e73eaee345e1ee67c23eace8895ed499693)
    
    Resolves: #1752050
    
    patch_name: 0225-ask-password-prevent-buffer-overrow-when-reading-fro.patch
    present_in_specfile: true
    location_in_specfile: 225
    squash_commits: true