From: Zack Rusin <zackr@vmware.com>
To: "willy@infradead.org" <willy@infradead.org>
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Subject: Re: [PATCH] mm: Fix a null ptr deref with CONFIG_DEBUG_VM enabled in wp_page_reuse
Date: Wed, 27 Jul 2022 19:31:34 +0000 [thread overview]
Message-ID: <66333fb601dfd3e487e856156988d91c05d94d9b.camel@vmware.com> (raw)
In-Reply-To: <YuGQ9tJPUcqnqvAV@casper.infradead.org>
On Wed, 2022-07-27 at 20:24 +0100, Matthew Wilcox wrote:
> On Wed, Jul 27, 2022 at 03:14:07PM -0400, Zack Rusin wrote:
> > From: Zack Rusin <zackr@vmware.com>
> >
> > Write page faults on last references might not have a valid page anymore.
> > wp_page_reuse has always dealt with that scenario by making
> > sure the page isn't null (or the reference was shared) before doing
> > anything with it. Recently added checks in VM_BUG_ON (enabled by the
> > CONFIG_DEBUG_VM option) use PageAnon helpers which assume the passed
> > page is never null, before making sure there is a valid page to work
> > with.
> >
> > Move the VM_BUG_ON, which unconditionally uses the page, after the
> > code that checks that we have a valid one.
>
> Message-ID: <CAHk-=wh_TrgNm6vz7=7CgZppr0UrZ9TwLyb3dgPXyG-w=a8kJQ@mail.gmail.com>
Ah, great, thanks.
z
prev parent reply other threads:[~2022-07-27 19:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-27 19:14 [PATCH] mm: Fix a null ptr deref with CONFIG_DEBUG_VM enabled in wp_page_reuse Zack Rusin
2022-07-27 19:24 ` Matthew Wilcox
2022-07-27 19:31 ` Zack Rusin [this message]
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