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SubjectRe: rm-ing files with open file descriptors
Date
From
Miquel van Smoorenburg <miquels@cistron.nl> said:

[...]

> It results in:
>
> link("/proc/self/fd/3", "flink-test2.txt") = -1 EXDEV (Invalid cross-device lin
> k)
>
> This is probably because link() doesn't look up the target of the
> symlink, it links the symlink itself. Linux allows symlinks with
> a nlink count of 2:
>
> % ln -s a b
> % ln b c
> ln: `b': warning: making a hard link to a symbolic link is not portable
> % ls -l
> lrwxrwxrwx 2 miquels staff 1 Jan 19 11:34 b -> a
> lrwxrwxrwx 2 miquels staff 1 Jan 19 11:34 c -> a
>
> This could be hacked around ofcourse in fs/namei.c, so I tried
> it for fun. And indeed, with a minor correction it works:
>
> % perl flink.pl
> Success.
>
> I now have a flink-test2.txt file. That is pretty cool ;)

This is a possible security risk: The unlinking program thinks the file is
forever inaccessible, but it isn't...
--
Horst von Brand http://counter.li.org # 22616
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