linux-kernel - Re: [PATCH] mm: kmsan: Panic on failure to allocate early boot metadata

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Message-ID: <CANpmjNNq9X+n=WFsa-p31gKJG5vLH6PXGmLt0eEmWoHwMN0scg@mail.gmail.com>
Date:   Mon, 16 Oct 2023 09:24:37 +0200
From:   Marco Elver <elver@...gle.com>
To:     Pedro Falcato <pedro.falcato@...il.com>
Cc:     kasan-dev@...glegroups.com,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: kmsan: Panic on failure to allocate early boot metadata

On Sun, 15 Oct 2023 at 22:35, Pedro Falcato <pedro.falcato@...il.com> wrote:
>
> On Sun, Oct 15, 2023 at 9:26 PM Pedro Falcato <pedro.falcato@...il.com> wrote:
> >
> > Given large enough allocations and a machine with low enough memory (i.e
> > a default QEMU VM), it's entirely possible that
> > kmsan_init_alloc_meta_for_range's shadow+origin allocation fails.
>
> Ugh, forgot to run checkpatch.pl until it was too late :/
>
> > Instead of eating a NULL deref kernel oops, check explicitly for memblock_alloc()
>
> If there's no need for a v2, please wrap the above line and...

Probably easier to send v2.

Otherwise looks good.

> > failure and panic with a nice error message.
> >
> > Signed-off-by: Pedro Falcato <pedro.falcato@...il.com>
> > ---
> >  mm/kmsan/shadow.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c
> > index 87318f9170f..3dae3d9c0b3 100644
> > --- a/mm/kmsan/shadow.c
> > +++ b/mm/kmsan/shadow.c
> > @@ -285,12 +285,18 @@ void __init kmsan_init_alloc_meta_for_range(void *start, void *end)
> >         size = PAGE_ALIGN((u64)end - (u64)start);
> >         shadow = memblock_alloc(size, PAGE_SIZE);
> >         origin = memblock_alloc(size, PAGE_SIZE);
> > +
> > +       if (!shadow || !origin)
> > +               panic("%s: Failed to allocate metadata memory for early boot range "
> > +                     "of size %llu",
>
> unwrap this string like this:
>     "%s: Failed to allocate metadata memory for early boot range of size %llu",
>
> Silly mistake...
>
> --
> Pedro