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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id s2-20020a0cdc02000000b0065af9d1203dsm693210qvk.121.2023.11.23.10.02.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Nov 2023 10:02:23 -0800 (PST) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: peterx@redhat.com, Andrew Morton , Dan Williams , Mel Gorman , Matthew Wilcox , "Aneesh Kumar K . V" , Christoph Hellwig Subject: [PATCH] mm/gup: Fix follow_devmap_p[mu]d() on page==NULL handling Date: Thu, 23 Nov 2023 13:02:22 -0500 Message-ID: <20231123180222.1048297-1-peterx@redhat.com> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on howler.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (howler.vger.email [0.0.0.0]); Thu, 23 Nov 2023 10:02:31 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1783378807507962092 X-GMAIL-MSGID: 1783378807507962092 This is a bug found not by any report but only by code observations. When GUP sees a devpmd/devpud and if page==NULL is returned, it means a fault is probably required. Here falling through when page==NULL can cause unexpected behavior. Fix both cases by catching the page==NULL cases with no_page_table(). Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings") Fixes: 080dbb618b4b ("mm/follow_page_mask: split follow_page_mask to smaller functions.") Cc: Dan Williams Cc: Mel Gorman Cc: Matthew Wilcox Cc: Aneesh Kumar K.V Cc: Christoph Hellwig Signed-off-by: Peter Xu Acked-by: David Hildenbrand --- mm/gup.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/gup.c b/mm/gup.c index 231711efa390..0a5f0e91bfec 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -710,6 +710,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, spin_unlock(ptl); if (page) return page; + return no_page_table(vma, flags); } if (likely(!pmd_trans_huge(pmdval))) return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); @@ -758,6 +759,7 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma, spin_unlock(ptl); if (page) return page; + return no_page_table(vma, flags); } if (unlikely(pud_bad(*pud))) return no_page_table(vma, flags);