busybox ash echo weirdness

[agowa]

Your Windows build number

Microsoft Windows [Version 10.0.17650.1001]

What you're doing and what's happening

Within Alpine Linux as root (busybox ash):

wget https://raw.githubusercontent.com/jirutka/alpine-make-rootfs/v0.1.0/alpine-make-rootfs
echo '714a764b96442f551084fc50941fd1352e15ca6d  alpine-make-rootfs' | sha1sum -c

What's wrong / what should be happening instead

2nd command fails with can't set tty process group (Operation not permitted)

Used wsl userland: Alpine
Used shell: ash
Symlinks in the system:
/bin/echo => /bin/busybox
/bin/ash => /bin/busybox

but it is not a problem of busybox, as doing all of the following works:

ash -c "echo '714a764b96442f551084fc50941fd1352e15ca6d  alpine-make-rootfs'" | sha1sum -c
/bin/echo '714a764b96442f551084fc50941fd1352e15ca6d  alpine-make-rootfs' | sha1sum -c
busybox echo '714a764b96442f551084fc50941fd1352e15ca6d  alpine-make-rootfs' | sha1sum -c

also using zsh or bash instead of ash

Strace of the failing command

gist

[therealkenc]

I don't have an Alpine setup handy (I'll look next time I do), but here's the fail, anyway. You might want to make sure you've used strace -f -o and post a gist for legibility. I would have expected to see PIDs in the first column. Hesitate to speculate (but have a hunch).

rt_sigprocmask(SIG_BLOCK, ~[], [], 8)   = 0
fork()                                  = 79
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=79, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
rt_sigreturn({mask=[]})                 = 0
setpgid(79, 79)                         = -1 ESRCH (No such process)
close(4)                                = 0
stat("/sbin/sha1sum", 0x7fffe4f74ad8)   = -1 ENOENT (No such file or directory)
stat("/bin/sha1sum", 0x7fffe4f74ad8)    = -1 ENOENT (No such file or directory)
stat("/usr/sbin/sha1sum", 0x7fffe4f74ad8) = -1 ENOENT (No such file or directory)
stat("/usr/bin/sha1sum", {st_mode=S_IFREG|0755, st_size=805024, ...}) = 0
rt_sigprocmask(SIG_BLOCK, ~[], [], 8)   = 0
fork() ash:                                  can't set tty process group (Operation not permitted)= 80

rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=80, si_uid=0, si_status=2, si_utime=0, si_stime=0} ---
rt_sigreturn({mask=[]})                 = 0
setpgid(80, 79)                         = -1 ESRCH (No such process)
close(3)                                = 0
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], WSTOPPED, NULL) = 79
wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 2}], WSTOPPED, NULL) = 80
ioctl(10, TIOCSPGRP, [78])              = 0
wait4(-1, 0x7fffe4f74b7c, WNOHANG|WSTOPPED, NULL) = -1 ECHILD (No child process)

[Biswa96]

@agowa338 Yes, that second command does not work. But if you change a little it then works. Try this:

wget https://raw.githubusercontent.com/jirutka/alpine-make-rootfs/v0.1.0/alpine-make-rootfs
echo '714a764b96442f551084fc50941fd1352e15ca6d  alpine-make-rootfs' > test.txt
sha1sum -c test.txt

[agowa]

I tried to generate a new strace file, but as soon as I specify the "-f" option it works. So I'm unable to provide a strace -f -o output, but I can provide a strace -o output. But I doubt it will be much different than the one from above
pipeError.log

@Biswa96 This is currently not a blocking bug for me. I just discovered it and would like to have it fixed. But thanks anyway for that workaround.

[therealkenc]

I just discovered it and would like to have it fixed.

If you don't hear different, keep one eye on #2786 / #1353. It might be working under strace because the child stays alive just long enough.

[therealkenc]

I got something today that might be related. This was on 17661 and Ubuntu 16.04.

63    waitid(P_PID, 13, {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=13, si_uid=0, si_status=213, si_utime=0, si_stime=0}, WEXITED, NULL) = 0
63    waitid(P_ALL, 0, 0x7ffffc491380, WNOHANG|WEXITED|WNOWAIT, NULL) = -1 ECHILD (No child processes)
63    clock_gettime(CLOCK_MONOTONIC, {233, 656312000}) = 0
63    epoll_wait(4,  <unfinished ...>
62    +++ killed by SIGKILL +++

I don't have a repro anyone wants to hear. The catch is in my case, that SIGKILL causes a blue screen. I sent a minidump to secure@microsoft.com and poked @benhillis.

[therealkenc]

@agowa338 - please try build 17713 and see if it addresses your issue with ash on Alpine.

[knottio]

@therealkenc I had this same issue on Alpine prior to build 17713. Updating to 17713 fixed it.

[therealkenc]

Right thanks for the heads up. My suspicion was correct and this was Rick Grimes problem. Duping for closure.