Re: [RFC][PATCH] sysctl: Remove the sysctl system call

Kees Cook [off-list ref] writes:

On Tue, Oct 01, 2019 at 01:36:32PM -0500, Eric W. Biederman wrote:

quoted

This system call has been deprecated almost since it was introduced, and
in a survey of the linux distributions I can no longer find any of them
that enable CONFIG_SYSCTL_SYSCALL.  The only indication that I can find
that anyone might care is that a few of the defconfigs in the kernel
enable CONFIG_SYSCTL_SYSCALL.  However this appears in only 31 of 414
defconfigs in the kernel, so I suspect this symbols presence is simply
because it is harmless to include rather than because it is necessary.

As there appear to be no users of the sysctl system call, remove the
code.  As this removes one of the few uses of the internal kernel mount
of proc I hope this allows for even more simplifications of the proc
filesystem.

I'm for it. :) I tripped over this being deprecated over a decade ago. :P

I think you can actually take this further and remove (or at least
empty) the uapi/linux/sysctl.h file too.

I copied everyone who had put this into a defconfig and I will wait a
little more to see if anyone screams.  I think it is a safe guess that
several of the affected configurations are dead (or at least
unmaintained) as I received 17 bounces when copying everyone.

I would make it a followup that removes uapi/linux/sysctl.h.  I don't
see anything in it that isn't about the sysctl system call.  I will keep
it a separate patch as I can imagine something silly that needs the
header file to compile.  A separate patch would make a revert easier
if we find something like that.

Eric