Bug#975104: openssh-client: ssh cannot be interrupted at "debug1: pledge: network"

Package: openssh-client
Version: 1:8.4p1-2
Severity: normal

I get the following:

zira:~> /usr/bin/ssh -vvv gcc202.fsffrance.org
OpenSSH_8.4p1 Debian-2, OpenSSL 1.1.1h  22 Sep 2020
[...]
debug1: Authentication succeeded (publickey).
Authenticated to gcc202.fsffrance.org ([195.170.63.224]:22).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network

and at this point, ssh is stuck. This is probably a server side issue,
but on the client side, I want to interrupt it. Neither Ctrl-C, Ctrl-\
nor [Return]~. works.

Here's the backtrace:

0x00007f65de8097c6 in __GI___select (nfds=7, readfds=0x55d3fbfb6f90, 
    writefds=0x55d3fbfc4100, exceptfds=0x0, exceptfds@entry=0x7ffcb7d05ed0, 
    timeout=timeout@entry=0x7ffcb7d05ed0)
    at ../sysdeps/unix/sysv/linux/select.c:41
41      ../sysdeps/unix/sysv/linux/select.c: No such file or directory.
(gdb) bt
#0  0x00007f65de8097c6 in __GI___select (nfds=7, readfds=0x55d3fbfb6f90, 
    writefds=0x55d3fbfc4100, exceptfds=0x0, exceptfds@entry=0x7ffcb7d05ed0, 
    timeout=timeout@entry=0x7ffcb7d05ed0)
    at ../sysdeps/unix/sysv/linux/select.c:41
#1  0x000055d3fbe1b1e7 in client_wait_until_can_do_something (
    rekeying=<optimized out>, nallocp=0x7ffcb7d05eb4, maxfdp=0x7ffcb7d05eb0, 
    writesetp=0x7ffcb7d05ec0, readsetp=0x7ffcb7d05eb8, ssh=0x55d3fbfb7590)
    at ../../clientloop.c:562
#2  client_loop (ssh=ssh@entry=0x55d3fbfb7590, have_pty=1, 
    escape_char_arg=<optimized out>, ssh2_chan_id=ssh2_chan_id@entry=0)
    at ../../clientloop.c:1368
#3  0x000055d3fbe0dd4d in ssh_session2 (pw=<optimized out>, ssh=0x55d3fbfb7590)
    at ../../ssh.c:2192
#4  main (ac=<optimized out>, av=<optimized out>) at ../../ssh.c:1687
quit) 

-- System Information:
Debian Release: bullseye/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'stable-updates'), (500, 'unstable'), (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 5.9.0-2-amd64 (SMP w/8 CPU threads)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=POSIX, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages openssh-client depends on:
ii  adduser           3.118
ii  dpkg              1.20.5
ii  libc6             2.31-4
ii  libedit2          3.1-20191231-1
ii  libfido2-1        1.5.0-2
ii  libgssapi-krb5-2  1.17-10
ii  libselinux1       3.1-2+b1
ii  libssl1.1         1.1.1h-1
ii  passwd            1:4.8.1-1
ii  zlib1g            1:1.2.11.dfsg-2

Versions of packages openssh-client recommends:
ii  xauth  1:1.0.10-1

Versions of packages openssh-client suggests:
pn  keychain      <none>
pn  libpam-ssh    <none>
pn  monkeysphere  <none>
ii  ssh-askpass   1:1.2.4.1-10+b1

-- no debconf information