Package: user-mode-linux Version: 4.19-1um-1+deb10u1+b1 Severity: normal File: /usr/bin/linux.uml Tags: upstream
CCing putty@p.d.o because this makes the user-mode-linux example in the psusan manpage not work. Steps to reproduce: Put the attached scripts "psusan-uml" and "psusan-uml-inside" in a directory and make them executable. Run ./psusan-uml in a terminal. Wait for the inital "read(0, " (from strace cat) to appear. Type something. Observed behaviour: Nothing happens. The input is not read. Pressing ^D will terminate the session, but the inner cat never sees the input. Expected behaviour: cat reads what you type and you see it appear in strace, and be echoed. Workaround: Arrange not to write anything into linux.uml until some output has appeared. That seems to work OK for me, leading me to think it's not a general lossage bug, but only happens if there is input to be read when linux.uml starts up its consoles. Notes: Commenting out "echo initial" makes it work, showing that this is a race. The |cat at the end is because linux.uml sets the fds it is using for a console to nonblocking. cat objects to that. So we pipe the stdout too, so that linux.uml does not set the actual tty to nonblocking. -- System Information: Debian Release: 10.10 APT prefers stable-debug APT policy: (500, 'stable-debug'), (500, 'stable') Architecture: amd64 (x86_64) Foreign Architectures: i386, armhf Kernel: Linux 5.6.0-1-amd64 (SMP w/8 CPU cores) Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE=C.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Init: sysvinit (via /sbin/init) LSM: AppArmor: enabled Versions of packages user-mode-linux depends on: ii libc6 2.28-10 Versions of packages user-mode-linux recommends: ii uml-utilities 20070815.2-1 Versions of packages user-mode-linux suggests: ii pterm [x-terminal-emulator] 0.75-3 pn rootstrap <none> pn slirp <none> pn user-mode-linux-doc <none> pn vde2 <none> ii xfce4-terminal [x-terminal-emulator] 0.8.7.4-2 ii xterm [x-terminal-emulator] 344-1+deb10u1 -- no debconf information
#!/bin/bash stty=`stty -g` trap 'stty "$stty"' 0 ( echo initial cat ) | \ bwrap --dev-bind / / --tmpfs /dev/shm \ linux.uml rootfstype=hostfs rootflags=/ rw \ con=fd:0,fd:1 \ init=$PWD/psusan-uml-inside 2>&1 \ | cat
#!/bin/bash # Set up vital pseudo-filesystems set -x mount -t proc none /proc exec 3<>/dev/tty1 stty raw -echo <&3 echo $PATH PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin export PATH stty -a >&2 strace cat
