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SubjectRe: rm-ing files with open file descriptors
On Sat, 19 Jan 2002, Horst von Brand wrote:
> Miquel van Smoorenburg <miquels@cistron.nl> said:
> [...]
> > It results in:
> > link("/proc/self/fd/3", "flink-test2.txt") = -1 EXDEV (Invalid cross-device link)
> > 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...
Will the ability to access this linked file still be there across
a reboot ? Or an fsck ? Tia , JimL

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