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Subject: Re: [PATCH v2 2/5] pid: add pidfd_open()
From:   =?ISO-8859-1?Q?J=FCrg?= Billeter <j@bitron.ch>
To:     Christian Brauner <christian@brauner.io>, jannh@google.com,
        luto@kernel.org, dhowells@redhat.com, serge@hallyn.com,
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Date:   Sat, 30 Mar 2019 12:53:57 +0100
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         <20190329155425.26059-3-christian@brauner.io>
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On Fri, 2019-03-29 at 16:54 +0100, Christian Brauner wrote:
> diff --git a/include/uapi/linux/wait.h b/include/uapi/linux/wait.h
> index ac49a220cf2a..d6c7c0701997 100644
> --- a/include/uapi/linux/wait.h
> +++ b/include/uapi/linux/wait.h
> @@ -18,5 +18,7 @@
>  #define P_PID		1
>  #define P_PGID		2
>  
> +/* Get a file descriptor for /proc/<pid> of the corresponding pidfd
> */
> +#define PIDFD_GET_PROCFD _IOR('p', 1, int)
>  
>  #endif /* _UAPI_LINUX_WAIT_H */

This is missing an entry in Documentation/ioctl/ioctl-number.txt and is
actually conflicting with existing entries.

However, I'd actually prefer a syscall to allow strict whitelisting via
seccomp and avoid the other ioctl disadvantages that Daniel has already
mentioned.

Cheers,
Jürg