Quoting Eric W. Biederman (ebied...@xmission.com):
> "Timofey.Kirillov" <distorh...@gmail.com> writes:
>
> > Hi,
> >
> > I have a question about using unnamed pipes with procfs.
> >
> > Suppose a chrooted environment with proc mounted as procfs. I am trying
> > to use bash process substitution feature and get this:
> >
> > $ cat <(echo hello)
> > cat: /dev/fd/63: No such file or directory
> >
> > While on the normal system:
> > $ cat <(echo hello)
> > hello
> >
> > As I understand, the problem is that when fuse making getattr on file
> > '/dev/fd/63' - it determines that it is symlink. The next step is
> > readlink, which gives something like that: /25977/fd/63 =>
> > pipe:[3087676]. And at the final step getattr on file
> > '/25977/fd/pipe:[3087676]' gives no such file or directory.
> >
> > Actually I encouter this issue while working on my own similar fuse proc
> > (for jail environments). Then I find procfs, tried it out and get the
> > same failure.
> >
> > I am tried to change logic of getattr in the next way. First make normal
> > stat of file. If it is not S_ISFIFO - make lstat. In that way the
> > process hangs forever on open syscall:
> > $ strace cat <(echo hello)
> > ...
> > open("/dev/fd/63", O_RDONLY
> >
> >
> > Is there any workaround of this problem?
>
> Check to see if /dev/fd is a symlink to /proc/self/fd
>
> If that symlink is missing magic using /dev/fd will fail. I suspect
> that for some reason your /dev/fd symlink simply has not been created in
> /dev.
Eric,
I believe he is using a fuse fs called 'procfs' which isn't properly
handling readlink.
Timofey, can you confirm?
-serge
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