Broken su in current - trying to fix myself, help needed!
David Xu
davidxu at FreeBSD.org
Thu Oct 18 01:29:12 PDT 2007
Artem Kuchin wrote:
> Hello!
>
> I really not at all good at any kind of system programming
> in FreeBSD or Un*x, but since my contacts with last commited
> of su could not be establish i decided to look at it myself.
>
> If you don't know what is the problem i'll describe it shortly:
>
> if you try to run a very simple perl script:
>
> #!/usr/bin/perl
> $com="/usr/bin/su root -c 'echo heck'";
> system($com);
> print "done!\n";
>
> it will print heck
>
> and then
>
> Suspended (tty output)
>
> and will hang in memory untill you type
> fg
>
> then you get
>
> done!
>
>
> I am working in csh, but i tested it in sh - result is
> the same. FreeBSD version is 7-PRERELEASE.
>
>
> So, I fetched su v. 1.76 from 6.2-STABLE and compiled it - it works
> like a charm. SO, i decided to figure what fails in 1.86.
>
> There are such like in the default: dection of switch
>
> child_pgrp = getpgid(child_pid);
> if (tcgetpgrp(STDERR_FILENO) == child_pgrp)
> tcsetpgrp(STDERR_FILENO, getpgrp());
>
>
> The problem is here.
> getpgid(child_pid) simply fails with errno 3 (process doesn't exist)
> and tcgetpgrp(STDERR_FILENO) return 100000 (can it be THAT high? i though
> it is only in 0-65535 range).
>
> The weird thing is that if i just comment out those lines like this
>
> /* child_pgrp = getpgid(child_pid);
> if (tcgetpgrp(STDERR_FILENO) == child_pgrp) */
> tcsetpgrp(STDERR_FILENO, getpgrp());
>
> su starts working again just fine.
>
> Any idea why getpgid fails and why tcgetpgrp return 100000 (always the same
> number)? What will brak if i leave these lines commented?
>
> --
> Regards,
> Artem
file su.c, line 472 may be incorrect since line 456 is a while loop
which only
exits if child process is exited. just remove line 472 and 473 to see if
problem
is fixed.
Regards,
David Xu
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