Re: [PATCH] pidfd: show pids for nested pid namespaces in fdinfo

[Christian Brauner]

On Tue, Oct 08, 2019 at 03:36:37PM +0200, Christian Kellner wrote:
> From: Christian Kellner <christian@xxxxxxxxxx>
> 
> The fdinfo file for a process file descriptor already contains the
> pid of the process in the callers namespaces. Additionally, if pid
> namespaces are configured, show the process ids of the process in
> all nested namespaces in the same format as in the procfs status
> file, i.e. "NSPid:\t%d\%d...". This allows the easy identification
> of the processes in nested namespaces.
> 
> Signed-off-by: Christian Kellner <christian@xxxxxxxxxx>

Yeah, makes sense to me.
Note that if you send the pidfd to a sibling pid namespace NSpid won't
show you anything useful. But that's what I'd expect security wise. You
should only be able to snoop on descendant pid namespaces.

Please add a test for this to verify that this all works correctly and
then resend. The tests live in tools/testing/selftests/pidfd/ and should
already have most of the infrastructure there. The fdinfo parsing code
should be in samples/pidfd/ which

For the patch itself:

Reviewed-by: Christian Brauner <christian.brauner@xxxxxxxxxx>

You can resend with my Reviewed-by retained if you don't change
anything. Before I see tests I'll hold off on merging this. ;)

Thanks!
Christian