Re: install.sh is wrong with libc.so

[Laurent Bercot <ska-dietlibc@skarnet.org>]

> umask 077
> cat < lib/libc.so > /lib/libc.so.tmp.pid # /lib/libc.so.tmp.pid is created with mode 600
> mv -f /lib/libc.so.tmp.pid /lib/libc.so
> chmod 755 /lib/libc.so # failed with "Permission denied"

  Very funny bug ^^
  I'm curious of the thought process behind that code:
  - why cat instead of cp ? I guess it's to avoid the implementation-defined behaviour
of cp wrt. rights of the destination file, whereas >'s behaviour is guaranteed.
  - but an explicit chmod is needed anyway.
  - why perform the chmod after the mv, since mv is guaranteed to be a rename() in that
case, the rights will be preserved ? Is there a possibility of someone abusing the
temp file if it is 0755, knowing it is owned by root anyway ?

  chmoding the temp file before the mv -f, instead of /lib/libc.so at the end, looks
like the obvious and simplest fix, but I'm wondering whether I missed something.

-- 
  Laurent