[RFC PATCH] ptrace: add PTRACE_GETFD request

Tycho Andersen tycho at tycho.ws
Fri Dec 6 14:10:45 UTC 2019

On Thu, Dec 05, 2019 at 11:44:53PM +0000, Sargun Dhillon wrote:
> PTRACE_GETFD is a generic ptrace API that allows the tracer to
> get file descriptors from the traceee.
> The primary reason to use this syscall is to allow sandboxers to

I might change this to "one motivation to use this ptrace command",
because I'm sure people will invent other crazy uses soon after it's
added :)

> take action on an FD on behalf of the tracee. For example, this
> can be combined with seccomp's user notification feature to extract
> a file descriptor and call privileged syscalls, like binding
> a socket to a privileged port.

This can already be accomplished via injecting parasite code like CRIU
does; adding a ptrace() command like this makes it much nicer to be
sure, but it is redundant.


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