[Buildroot] [RFC 0/2] Handle conflicting files with Busybox

[Yann E. MORIN <yann.morin.1998@free.fr>]

Baruch, Thomas, All,

On 2017-12-28 20:01 +0200, Baruch Siach spake thusly:
> On Thu, Dec 28, 2017 at 06:20:30PM +0100, Yann E. MORIN wrote:
> > On 2017-12-28 18:04 +0100, Thomas Petazzoni spake thusly:
[--SNIP--]
> > > There is however one remaining debate: my patch series tweaks the
> > > Busybox configuration to not build the support for applets for which
> > > the functionality is provided by a full-featured program. But Baruch
> > > didn't like this tweaking of the Busybox configuration, and would
> > > prefer to not install the symlinks, and leave the Busybox configuration
> > > unchanged (which means we have lots of Busybox applets built into
> > > Busybox that are not really used on the target).
> > > 
> > > Do you have an opinion on this specific topic ?
> > 
> > I prefer they be explicitly disabled as you did.
> 
> As I said earlier, I don't like this heavy handed modification of the Busybox 
> configuration. I'm not sure how robust this solution would be, as there might 
> be unintended consequences. Kconfig 'select' and 'depends' contribute to that. 
> I prefer to keep config modifications to minimum.

Agreed that the 'select' things in busybox' Kconfig could be an issue.
But do we have applets that get select-ed by another?

In current busybox, there is no applet that is select-ed:

    $ git grep -E 'config:[[:space:]]+\<select ' |cut -d : -f 2- |sort -u
    //config:select FEATURE_BZIP2_DECOMPRESS
    //config:se     lect FEATURE_GZIP_DECOMPRESS
    //config:select FEATURE_IP_ADDRESS
    //conf  ig:select FEATURE_IP_LINK
    //config:select FEATURE_IP_NEIGH
    //config:           select FEATURE_IP_ROUTE
    //config:select FEATURE_IP_RULE
    //config:sele       ct FEATURE_IP_TUNNEL
    //config:select FEATURE_SEAMLESS_GZ
    //config:sel        ect FEATURE_SYSLOG
    //config:select LONG_OPTS
    //config:select PLATFORM        _LINUX
    //config:select PLATFORM_LINUX # statfs()
    //config:select PLAT        FORM_LINUX #sysinfo()
    //config:select TLS
    //config:select VOLUMEID

None of those are actual applets.

But OK, there is no guarantee that this will continue to be the case.

As an aside, we currently disable a bunch of Busybox options, of which
only three applets: swapon, swapoff, ash.

> > First, because this is a security issue that there is dead code: these
> > applets are still usable by calling 'busybox foo' for example, and that
> > is a security issue.
> 
> That is no different than the current behaviour.

Indeed not really.

But it's not because we're doing something bad today, that we should
pursue in this direction! ;-)

In the end, my preference is still to do as Thomas proposed...

Regards,
Yann E. MORIN.

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