Re: [PATCH, RESEND] procfs: silence lockdep warning about read vs. exec seq_file

[Eric W. Biederman]

"Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> writes:

> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
>
> Testcase:
>
>   cat /proc/self/maps >/dev/null
>   chmod +x /proc/self/net/packet
>   exec /proc/self/net/packet
>
> It triggers lockdep warning:

> I don't know why we allow "chmod +x" on some proc files, notably net-related.
> Is it a bug?

It looks like we simply did not remove the ability to make those files
executable when we realized executable proc files could be a problem.

I expect that part of proc could use an audit where someone figures out
what makes sense.  It does appear that chmod XXX /proc/generic_file
is explicitly supported.  So we would have to be delicate with any
changes in that area to avoid creating userspace regressions.

Eric
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