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:

quoted

On Thu, Sep 10, 2020 at 08:38:21PM +0200, Mickaël Salaün wrote:

quoted

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 -