Catalin Marinas [off-list ref] writes:

On Thu, Jul 23, 2020 at 10:25:35PM +0200, Thomas Gleixner wrote:

quoted

Andrei Vagin [off-list ref] writes:

quoted

On Wed, Jul 22, 2020 at 07:15:06PM +0100, Catalin Marinas wrote:

I don't think that we need to handle this case in the kernel. Users
must understand what they are doing and have to write code so that avoid
these sort of situations. In general, I would say that in most cases it
is a bad idea to call setns from a signal handler.

This should not be supported in the first place and just let the
offender die right there.

It would have been nice if we caught the offender easily but since
signal handling doesn't have to be paired with sigreturn(), the kernel
can't tell whether setns() is called in the wrong context. I guess we
just have to live with this (maybe document the restriction in
time_namespaces(7) or setns(2)).

Yes, I know that it's more or less impossible. The 'should' was just
wishful thinking :)

But yes, proper documentation is required.

Thanks,

        tglx

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