linux-kernel - Re: [PATCH][CFT] [coredump] don't use __kernel_write() on kmap_local

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Message-ID: <CAMuHMdUTHi35MwFt=x+soc1XdYH09DYfHxzjexKG8swR1K40Zw@mail.gmail.com>
Date:   Wed, 9 Nov 2022 14:57:08 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     sedat.dilek@...il.com,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "J. R. Okajima" <hooanon05g@...il.com>,
        Ira Weiny <ira.weiny@...el.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH][CFT] [coredump] don't use __kernel_write() on kmap_local_page()

Hi Al,

On Tue, Oct 4, 2022 at 8:19 AM Sedat Dilek <sedat.dilek@...il.com> wrote:
> On Tue, Oct 4, 2022 at 2:51 AM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> > On Mon, Oct 3, 2022 at 4:37 PM Al Viro <viro@...iv.linux.org.uk> wrote:
> > >
> > > One variant would be to revert the original patch, put its
> > > (hopefully) fixed variant into -next and let it sit there for
> > > a while.  Another is to put this incremental into -next and
> > > merge it into mainline once it gets a sane amount of testing.
> >
> > Just do the incremental fix. It looks obvious enough ("oops, we need
> > to get the pos _after_ we've done any skip-lseeks on the core file")
> > that I think it would be just harder to follow a "revert and follow up
> > with a fix".
> >
> > I don't think it needs a ton of extra testing, with Okajima having
> > already confirmed it fixes his problem case..
> >
> >                 Linus
>
> [ CC Geert ]
>
> There was another patch from Geert concerning the same coredump changes:
>
> [PATCH] coredump: Move dump_emit_page() to kill unused warning
>
> If CONFIG_ELF_CORE is not set:
>
>     fs/coredump.c:835:12: error: ‘dump_emit_page’ defined but not used
> [-Werror=unused-function]
>       835 | static int dump_emit_page(struct coredump_params *cprm,
> struct page *page)
>           |            ^~~~~~~~~~~~~~
>
> Fix this by moving dump_emit_page() inside the existing section
> protected by #ifdef CONFIG_ELF_CORE.
>
> Fixes: 06bbaa6dc53cb720 ("[coredump] don't use __kernel_write() on
> kmap_local_page()")
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>
> Please, check yourself!

The build issue is still present in today's linux-next.
Al, can you please apply my fix, so Greg can backport all of this to stable?
https://lore.kernel.org/all/YzxxtFSCEsycgXSK@kroah.com

Thanks!

> [1] https://lore.kernel.org/all/20221003090657.2053236-1-geert@linux-m68k.org/

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds