Re: [PATCH] credential syscalls only effect calling thread

["Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi Shawn

Thanks for the patch. By chance, I've just been doing some work
on updating the pages regarding exactly this point. My patches
go into rather more detail though, and include a new page,
nptl(7), that foes into some of the details. I'll CC you on
my request for review of that page, in case you'd like to make 
some comments.

Cheers,

Michael


On 03/21/2015 09:50 PM, Shawn Landden wrote:
> Signed-off-by: Shawn Landden <shawn-01I/ocv1qBBILuwUvNxBeQ@public.gmane.org>
> ---
>  man2/seteuid.2   | 4 ++++
>  man2/setfsgid.2  | 4 ++++
>  man2/setfsuid.2  | 4 ++++
>  man2/setgid.2    | 4 ++++
>  man2/setresuid.2 | 4 ++++
>  man2/setreuid.2  | 4 ++++
>  man2/setuid.2    | 4 ++++
>  7 files changed, 28 insertions(+)
> 
> diff --git a/man2/seteuid.2 b/man2/seteuid.2
> index 4690fd6..d482570 100644
> --- a/man2/seteuid.2
> +++ b/man2/seteuid.2
> @@ -138,6 +138,10 @@ are implemented as library functions that call, respectively,
>  .BR setreuid (2)
>  and
>  .BR setresgid (2).
> +
> +The syscall only sets the credentials of the calling thread. The glibc wrapper
> +sets up a signal handler so that it effects all threads. This means that you
> +can use the syscall directly to have differn't credentials on differn't threads.
>  .SH SEE ALSO
>  .BR geteuid (2),
>  .BR setresuid (2),
> diff --git a/man2/setfsgid.2 b/man2/setfsgid.2
> index d1d021d..1451b69 100644
> --- a/man2/setfsgid.2
> +++ b/man2/setfsgid.2
> @@ -120,6 +120,10 @@ least,
>  should be returned when the call fails (because the caller lacks the
>  .B CAP_SETGID
>  capability).
> +
> +The syscall only sets the credentials of the calling thread. The glibc wrapper
> +sets up a signal handler so that it effects all threads. This means that you
> +can use the syscall directly to have differn't credentials on differn't threads.
>  .SH SEE ALSO
>  .BR kill (2),
>  .BR setfsuid (2),
> diff --git a/man2/setfsuid.2 b/man2/setfsuid.2
> index 57b125e..e04ad78 100644
> --- a/man2/setfsuid.2
> +++ b/man2/setfsuid.2
> @@ -128,6 +128,10 @@ least,
>  should be returned when the call fails (because the caller lacks the
>  .B CAP_SETUID
>  capability).
> +
> +The syscall only sets the credentials of the calling thread. The glibc wrapper
> +sets up a signal handler so that it effects all threads. This means that you
> +can use the syscall directly to have differn't credentials on differn't threads.
>  .SH SEE ALSO
>  .BR kill (2),
>  .BR setfsgid (2),
> diff --git a/man2/setgid.2 b/man2/setgid.2
> index d9cccd5..0500961 100644
> --- a/man2/setgid.2
> +++ b/man2/setgid.2
> @@ -80,6 +80,10 @@ supporting 32-bit IDs.
>  The glibc
>  .BR setgid ()
>  wrapper function transparently deals with the variation across kernel versions.
> +
> +The syscall only sets the credentials of the calling thread. The glibc wrapper
> +sets up a signal handler so that it effects all threads. This means that you
> +can use the syscall directly to have differn't credentials on differn't threads.
>  .SH SEE ALSO
>  .BR getgid (2),
>  .BR setegid (2),
> diff --git a/man2/setresuid.2 b/man2/setresuid.2
> index 99ab94f..eb97a9d 100644
> --- a/man2/setresuid.2
> +++ b/man2/setresuid.2
> @@ -129,6 +129,10 @@ The glibc
>  and
>  .BR setresgid ()
>  wrapper functions transparently deal with the variations across kernel versions.
> +
> +The syscall only sets the credentials of the calling thread. The glibc wrapper
> +sets up a signal handler so that it effects all threads. This means that you
> +can use the syscall directly to have differn't credentials on differn't threads.
>  .SH SEE ALSO
>  .BR getresuid (2),
>  .BR getuid (2),
> diff --git a/man2/setreuid.2 b/man2/setreuid.2
> index c6597e9..844c5c4 100644
> --- a/man2/setreuid.2
> +++ b/man2/setreuid.2
> @@ -191,6 +191,10 @@ The glibc
>  and
>  .BR setregid ()
>  wrapper functions transparently deal with the variations across kernel versions.
> +
> +The syscall only sets the credentials of the calling thread. The glibc wrapper
> +sets up a signal handler so that it effects all threads. This means that you
> +can use the syscall directly to have differn't credentials on differn't threads.
>  .SH SEE ALSO
>  .BR getgid (2),
>  .BR getuid (2),
> diff --git a/man2/setuid.2 b/man2/setuid.2
> index c6f870e..6a90ae0 100644
> --- a/man2/setuid.2
> +++ b/man2/setuid.2
> @@ -142,6 +142,10 @@ supporting 32-bit IDs.
>  The glibc
>  .BR setuid ()
>  wrapper function transparently deals with the variation across kernel versions.
> +
> +The syscall only sets the credentials of the calling thread. The glibc wrapper
> +sets up a signal handler so that it effects all threads. This means that you
> +can use the syscall directly to have differn't credentials on differn't threads.
>  .SH SEE ALSO
>  .BR getuid (2),
>  .BR seteuid (2),
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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