From: Matthew Wilcox <willy@infradead.org>
To: Zack Rusin <zackr@vmware.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>, Jan Kara <jack@suse.cz>,
David Hildenbrand <david@redhat.com>, NeilBrown <neilb@suse.de>,
Yang Shi <shy828301@gmail.com>,
dri-devel@lists.freedesktop.org, Michal Hocko <mhocko@kernel.org>,
David Howells <dhowells@redhat.com>,
linux-mm@kvack.org, Khalid Aziz <khalid.aziz@oracle.com>,
Don Dutile <ddutile@redhat.com>, Christoph Hellwig <hch@lst.de>,
mombasawalam@vmware.com, Andrea Arcangeli <aarcange@redhat.com>,
Minchan Kim <minchan@kernel.org>, Rik van Riel <riel@surriel.com>,
Hugh Dickins <hughd@google.com>,
Liang Zhang <zhangliang5@huawei.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Jason Gunthorpe <jgg@nvidia.com>,
David Rientjes <rientjes@google.com>,
Pedro Demarchi Gomes <pedrodemargomes@gmail.com>,
Jann Horn <jannh@google.com>, John Hubbard <jhubbard@nvidia.com>,
Shakeel Butt <shakeelb@google.com>,
banackm@vmware.com, Muchun Song <songmuchun@bytedance.com>,
Peter Xu <peterx@redhat.com>,
Suren Baghdasaryan <surenb@google.com>,
Vlastimil Babka <vbabka@suse.cz>,
Hongchen Zhang <zhanghongchen@loongson.cn>,
Oleg Nesterov <oleg@redhat.com>,
krastevm@vmware.com, Nadav Amit <namit@vmware.com>,
Andrew Morton <akpm@linux-foundation.org>,
Roman Gushchin <guro@fb.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH] mm: Fix a null ptr deref with CONFIG_DEBUG_VM enabled in wp_page_reuse
Date: Wed, 27 Jul 2022 20:24:38 +0100 [thread overview]
Message-ID: <YuGQ9tJPUcqnqvAV@casper.infradead.org> (raw)
In-Reply-To: <20220727191407.1768600-1-zack@kde.org>
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>
next prev parent reply other threads:[~2022-07-27 19:24 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 [this message]
2022-07-27 19:31 ` Zack Rusin
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