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Message-ID: <20200910200543.GY6583@casper.infradead.org>
Date: Thu, 10 Sep 2020 21:05:43 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: Mickaël Salaün <mic@...ikod.net>,
Mimi Zohar <zohar@...ux.ibm.com>, linux-kernel@...r.kernel.org,
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Subject: Re: [RFC PATCH v9 0/3] Add introspect_access(2) (was O_MAYEXEC)
On Thu, Sep 10, 2020 at 09:00:10PM +0100, Al Viro wrote:
> On Thu, Sep 10, 2020 at 07:40:33PM +0100, Matthew Wilcox wrote:
> > On Thu, Sep 10, 2020 at 08:38:21PM +0200, Mickaël Salaün wrote:
> > > There is also the use case of noexec mounts and file permissions. From
> > > user space point of view, it doesn't matter which kernel component is in
> > > charge of defining the policy. The syscall should then not be tied with
> > > a verification/integrity/signature/appraisal vocabulary, but simply an
> > > access control one.
> >
> > permission()?
>
> int lsm(int fd, const char *how, char *error, int size);
>
> Seriously, this is "ask LSM to apply special policy to file"; let's
> _not_ mess with flags, etc. for that; give it decent bandwidth
> and since it's completely opaque for the rest of the kernel,
> just a pass a string to be parsed by LSM as it sees fit.
Hang on, it does have some things which aren't BD^W^WLSM. It lets
the interpreter honour the mount -o noexec option. I presume it's
not easily defeated by
cat /home/salaun/bin/bad.pl | perl -
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