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Message-ID: <87y2n55xzv.fsf@oldenburg2.str.redhat.com>
Date: Mon, 27 Jul 2020 07:27:00 +0200
From: Florian Weimer <fweimer@...hat.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: Mickaël Salaün <mic@...ikod.net>,
linux-kernel@...r.kernel.org, Aleksa Sarai <cyphar@...har.com>,
Alexei Starovoitov <ast@...nel.org>,
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Thibaut Sautereau <thibaut.sautereau@....gouv.fr>
Subject: Re: [PATCH v7 4/7] fs: Introduce O_MAYEXEC flag for openat2(2)
* Al Viro:
> On Thu, Jul 23, 2020 at 07:12:24PM +0200, Mickaël Salaün wrote:
>> When the O_MAYEXEC flag is passed, openat2(2) may be subject to
>> additional restrictions depending on a security policy managed by the
>> kernel through a sysctl or implemented by an LSM thanks to the
>> inode_permission hook. This new flag is ignored by open(2) and
>> openat(2) because of their unspecified flags handling. When used with
>> openat2(2), the default behavior is only to forbid to open a directory.
>
> Correct me if I'm wrong, but it looks like you are introducing a magical
> flag that would mean "let the Linux S&M take an extra special whip
> for this open()".
>
> Why is it done during open? If the caller is passing it deliberately,
> why not have an explicit request to apply given torture device to an
> already opened file? Why not sys_masochism(int fd, char *hurt_flavour),
> for that matter?
While I do not think this is appropriate language for a workplace, Al
has a point: If the auditing event can be generated on an already-open
descriptor, it would also cover scenarios like this one:
perl < /path/to/script
Where the process that opens the file does not (and cannot) know that it
will be used for execution purposes.
Thanks,
Florian
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