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bh=jNFq9DR9fflrZIbqu8UmHOJl+ac80dvlW2mJLqpUET4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oqxOPvncCYYsHc2zoO8qCejMi3nRQFIbfpDIa0vowBMc1z+WNsSPyP1juY/HY3PRP ZPjbfPYCVLMJm4bRRMCDuw0cFUjCjZkPmEDFaSlXOJNM/vAtzA19kLuI3qGD2wFU4i hUzXOMeH8J7AlDK6lMa7w5L4/Aczug++BKLkPBczDxZ8G8oz0e+oNHY7DbR3cUyEtS TM+EHsdsOIQ1ma5J5zGc3Oqzx5CMWZPosWDsHjak8H75aKgX3sG+heb83p9SQ7yY2/ 97PJjRCcUKoUdqnUFfK2B2nCg0lGT0dblNd0aCA+BCp87j5T/N5cCdoCFEQF83T92J 6uGeJENIJXqoA== From: SeongJae Park To: Lorenzo Stoakes Cc: David Hildenbrand , Marek Szyprowski , Kefeng Wang , akpm@linux-foundation.org, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, SeongJae Park Subject: Re: [PATCH -next 5/7] mm: memory: convert wp_page_copy() to use folios Date: Fri, 13 Jan 2023 22:16:06 +0000 Message-Id: <20230113221606.1370-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2F6B110000D X-Rspam-User: X-Stat-Signature: q8m3we97mr1kyjmhbeknc3aknbfx15jc X-HE-Tag: 1673648169-462617 X-HE-Meta: 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 7qJxVVHM 0+oN32WSKLZhi1E38/9ltDrdLVNfpnJUH5onwbAsycj/anCfXCsg8PpDitZXFoZuLX4K4gHIonl/Rm5vZ/jtUDsDEVZ13er0bSRdIHjip0oGUGBQvjPgvuqQu2w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello, On Fri, 13 Jan 2023 19:04:14 +0000 Lorenzo Stoakes wrote: > On Fri, Jan 13, 2023 at 02:08:36PM +0100, David Hildenbrand wrote: > > On 13.01.23 14:01, Marek Szyprowski wrote: > > > Hi > > > > > > On 12.01.2023 09:30, Kefeng Wang wrote: > > > > The old_page/new_page are converted to old_folio/new_folio in > > > > wp_page_copy(), then replaced related page functions to folio > > > > functions. > > > > > > > > Signed-off-by: Kefeng Wang > > > > > > This patch, merged into today's linux-next as commit 9ebae00c8e30 ("mm: > > > memory: convert wp_page_copy() to use folios"), causes serious stability > > > issues on my ARM based test boards. Here is the example of such crash: > > > > syzbot is also not happy: > > > > https://lkml.kernel.org/r/000000000000807c7805f2205df1@google.com > > > > -- > > Thanks, > > > > David / dhildenb > > > > This also completely broke my qemu environment. Same to me. > > In that thread Willy points out that the issue stems from blindly assigning > page_folio(old_page) to old_folio without checking whether it is NULL first, > therefore triggering a NULL pointer deref. > > A quick fix would be to put in a check (as shown below) which fixes the issue, > but as Willy said, I think we should drop this until it can be fixed in a > respin. > > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3044,7 +3044,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) > struct vm_area_struct *vma = vmf->vma; > struct mm_struct *mm = vma->vm_mm; > struct page *old_page = vmf->page; > - struct folio *old_folio = page_folio(old_page); > + struct folio *old_folio = old_page ? page_folio(old_page) : NULL; Tested-by: SeongJae Park Thanks, SJ