On Sep 25 2007 18:19, Miloslav Semler wrote:
quoted text
>> > > So what? Just do this: chdir into the root after chroot.
>> > >       
>> > I don't think so.  His exploit just got me all the way out of a chroot
>> > within a
>> > chroot within a chroot, inclusive of lots of chdirs.
>> >     
>>
>> Close all fds that point to directories outside the root ;-)
>>   
> This  does not help.  Let's try:
> chroot somewhere
> mkdir foo
> fd = open /
> chroot foo

('fd' implicitly closed and chdir to /foo)

quoted text
> fchdir fd

-EINVAL

quoted text
> chdir ".."

/../ => /

quoted text
> ....
> chdir ".."
> chroot "."
> so you are in root.

so we remain in chroot.
-
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