linux-kernel - Re: [PATCH v2] mm: fix a possible null pointer dereference in setup_zone

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Message-ID: <CANgpojUf53ncbYqQRmfMG6R9WYQHSyPGU=LkWVK-MonNDGa8gQ@mail.gmail.com>
Date: Thu, 7 Nov 2024 21:09:05 +0800
From: Qiu-ji Chen <chenqiuji666@...il.com>
To: David Hildenbrand <david@...hat.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, baijiaju1990@...il.com, stable@...r.kernel.org
Subject: Re: [PATCH v2] mm: fix a possible null pointer dereference in setup_zone_pageset()

Hello, the previous patch did not correctly check and release the
relevant pointers. Version 2 has fixed these issues. Thank you for
your response.


On Thu, Nov 7, 2024 at 8:53 PM David Hildenbrand <david@...hat.com> wrote:
>
> On 07.11.24 13:41, Qiu-ji Chen wrote:
> > The function call alloc_percpu() returns a pointer to the memory address,
> > but it hasn't been checked. Our static analysis tool indicates that null
> > pointer dereference may exist in pointer zone->per_cpu_pageset. It is
> > always safe to judge the null pointer before use.
> >
> > Signed-off-by: Qiu-ji Chen <chenqiuji666@...il.com>
> > Cc: stable@...r.kernel.org
> > Fixes: 9420f89db2dd ("mm: move most of core MM initialization to mm/mm_init.c")
> > ---
> > V2:
> > Fixed the incorrect code logic.
> > Thanks David Hildenbrand for helpful suggestion.
> > ---
> >   mm/page_alloc.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 8afab64814dc..7c8a74fd02d6 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -5703,8 +5703,14 @@ void __meminit setup_zone_pageset(struct zone *zone)
> >       /* Size may be 0 on !SMP && !NUMA */
> >       if (sizeof(struct per_cpu_zonestat) > 0)
> >               zone->per_cpu_zonestats = alloc_percpu(struct per_cpu_zonestat);
> > +     if (!zone->per_cpu_zonestats)
> > +             return;
> >
> >       zone->per_cpu_pageset = alloc_percpu(struct per_cpu_pages);
> > +     if (!zone->per_cpu_pageset) {
> > +             free_percpu(zone->per_cpu_zonestats);
> > +             return;
> > +     }
> >       for_each_possible_cpu(cpu) {
> >               struct per_cpu_pages *pcp;
> >               struct per_cpu_zonestat *pzstats;
>
> Unmodified patch, likely not what you wanted to send?
>
>
> --
> Cheers,
>
> David / dhildenb
>