Bug#1052451: openssh-client: Ctrl-C kills ssh but not ssh-add, which steals input from the terminal

On 2023-09-22 11:28:12 +0200, Vincent Lefevre wrote:
> It seems that that ssh command runs ssh-add automatically.
> While I did a Ctrl-C to interrupt ssh started by unison (for
> synchronization with a remote machine) from mutt, ssh-add is
> still running and attached to the terminal:
> 
> UID          PID    PPID  C STIME TTY          TIME CMD
> vlefevre    2129    2128  0 11:00 pts/5    00:00:04 mutt
> vlefevre    2358       1  0 11:03 pts/5    00:00:00 ssh-add [...]
> 
> and it steals input (typed keys) that should go to mutt.
> 
> Note: ssh-add was asking for a passphrase, and I did not want to
> enter it now. That's why I did Ctrl-C.

The current ssh-add backtrace shows successive calls to do_file,
add_file, read_passphrase, readpassphrase, read, __GI___libc_read.
So it is still trying to read a passphrase from the terminal.