Re: [RFC PATCH] kbuild: check uniqueness of basename of modules

[Kees Cook]

On Wed, May 15, 2019 at 04:53:15PM +0900, Masahiro Yamada wrote:
> On Wed, May 15, 2019 at 4:40 PM Masahiro Yamada
> <yamada.masahiro@xxxxxxxxxxxxx> wrote:
> >
> > In the recent build test of linux-next, Stephen saw a build error
> > caused by a broken .tmp_versions/*.mod file:
> >
> >   https://lkml.org/lkml/2019/5/13/991
> >
> > drivers/net/phy/asix.ko and drivers/net/usb/asix.ko have the same
> > basename, and there is a race in generating .tmp_versions/asix.mod
> >
> > Kbuild has not checked this before, and it occasionally shows up with
> > obscure error message when this kind of race occurs.
> >
> > It is not trivial to catch this potential issue by eyes.
> >
> > Hence, this script.
> >
> > I compile-tested allmodconfig for the latest kernel as of writing,
> > it detected the following:
> >
> > warning: same basename '88pm800.ko' if the following are built as modules:
> >   drivers/regulator/88pm800.ko
> >   drivers/mfd/88pm800.ko
> > warning: same basename 'adv7511.ko' if the following are built as modules:
> >   drivers/gpu/drm/bridge/adv7511/adv7511.ko
> >   drivers/media/i2c/adv7511.ko
> > warning: same basename 'asix.ko' if the following are built as modules:
> >   drivers/net/phy/asix.ko
> >   drivers/net/usb/asix.ko
> > warning: same basename 'coda.ko' if the following are built as modules:
> >   fs/coda/coda.ko
> >   drivers/media/platform/coda/coda.ko
> > warning: same basename 'realtek.ko' if the following are built as modules:
> >   drivers/net/phy/realtek.ko
> >   drivers/net/dsa/realtek.ko
> >
> > Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> > ---
> >
> 
> > diff --git a/scripts/modules-check.sh b/scripts/modules-check.sh
> > new file mode 100755
> > index 000000000000..944e68bd22b0
> > --- /dev/null
> > +++ b/scripts/modules-check.sh
> > @@ -0,0 +1,18 @@
> > +#!/bin/sh
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +# Warn if two or more modules have the same basename
> > +check_same_name_modules()
> > +{
> > +       same_name_modules=$(cat modules.order modules.builtin | \
> > +                               xargs basename -a | sort | uniq -d)

While probably it'll never be a problem, just for robustness, I'd add "--"
to the end basename to terminate argument interpretation:

    xargs basename -a -- | sort | ...

> > +
> > +       for m in $same_name_modules
> > +       do
> > +               echo "warning: same basename '$m' if the following are built as modules:"
> > +               grep --no-filename -e /$m modules.order modules.builtin | \
> > +                                                       sed 's:^kernel/:  :'
> 
> 
> Self nit-picking:
> It might be better to send these messages to stderr instead of stdout.

Yeah, wrapping a ">&2" around the report would be good. With these fixes:

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-- 
Kees Cook