Hacker News new | ask | show | jobs
by DmitriRavinoff 4389 days ago
Yes, but if you can't run the chmod binary...
3 comments
fjarlq 4389 days ago
No, root can still run chmod, because its superuser privileges override the new restrictive directory perms. That was my point.

Maybe the original problem was actually "chmod a-rwx /bin/chmod" ... That would mean even the superuser couldn't execute /bin/chmod anymore, so you'd have to do something more creative to reset the executable bit on /bin/chmod. Like compile a C program that calls the chmod system call, or:

  mv /bin/chmod /bin/chmod.orig
  cp -p /bin/ls /bin/chmod
  cp /bin/chmod.orig /bin/chmod
link
pantalaimon 4388 days ago
> Like compile a C program that calls the chmod system call

The compiler wouldn't be executable anymore either

link
claviola 4388 days ago
Yes, it would. Like he said, you can still run it unless you specifically removed its permissions.
link
mtdewcmu 4389 days ago
The explanation for what made him type that is what interests me. It would be like accidentally cutting your left hand clean off with a steak knife while you were eating dinner.
link
johnchristopher 4389 days ago
My bash is set to use vim bindings (set -o vi) and I constantly loop through commands. I am guilty of doing this while sleepy and sometimes I think I have cd to another directory when in fact I have not. I rm-ed (too) many things that way.
link
mtdewcmu 4388 days ago
I gave the vi mode a very short try, but it doesn't seem to make as much sense in a shell. If it has you accidentally deleting things, you might want to ask how much is it really worth. In vim you can undo.
link
r4um 4388 days ago
One can use the shared library loader to invoke binaries that do not have executable bit set, comes in handy once in a while.

  $ cp /bin/chmod .
  $ chmod -x ./chmod
  $ /lib/ld-2.19.so ./chmod
  ./chmod: missing operand
  Try './chmod --help' for more information.
link