From nobody Wed Apr 15 05:48:11 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9ACAAC43334 for ; Tue, 26 Jul 2022 06:27:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237947AbiGZG1t (ORCPT ); Tue, 26 Jul 2022 02:27:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45610 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237946AbiGZG1b (ORCPT ); Tue, 26 Jul 2022 02:27:31 -0400 Received: from mail-pg1-x52f.google.com (mail-pg1-x52f.google.com [IPv6:2607:f8b0:4864:20::52f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7E9F027B0A for ; Mon, 25 Jul 2022 23:25:33 -0700 (PDT) Received: by mail-pg1-x52f.google.com with SMTP id q22so7184747pgt.9 for ; Mon, 25 Jul 2022 23:25:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=AdOoxODJiumCfXGJPDqlgTRMx1Hwty97pt6JnuBcVOQ=; b=ie3eJ3v2MPmIgwvF18zCl0L7By+ZEHT6fvXB5MfvLLOglu2VNhWaFg0Aqpj4oWyFj/ of1Gi+hZUS/Vcz+B0hP6r8GYy5SVUp4JrJ0MxBXtBzTArlpIZCa9xkZ5jxuW97oFB3fr +RtPx5Oj2VyJT2fkx+KuSfmvZb8vBN2+ONNsazQcrLHqXnptWUSZe/Lc9LVzoUOt9qes 7wGiFnR0kuFDs5/fh25ZMN4wcE2DH3bwvifDn+sDUUnEvvpjFSk/MjVOaWHh0bdVtJny Z/czCq1xNx12UrAiJT1VP+uTjBZPt3D5o7F70keje9f+ldWFWS0qkXy1iw2IjqGBYANo KMYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=AdOoxODJiumCfXGJPDqlgTRMx1Hwty97pt6JnuBcVOQ=; b=oBtSmuA8QLNHUNnwjcSBSCsTL9uiXtLINjHiZnkxLwDeZINHE+Yy6pv9B3Hr/ar5pg kJ9TlpsDDJlajYLWEXtVYokIdu+0GglTY8iionxKvwW556qLofXRWlBoqUEUrdM0HuJg xlV3GKAk1LAkiZtoH0r9aLkvyhLkl9MWEGQtoJaSQ7J7aa+ep6m2TRvDFSXtWFev201X jWLJo63doeKEiMxns7K8NQE4i4lFvY8SYFMk9ossdSIxkOUbdF7otkrRfxMcwRy8Rcvi 8e/D0jjmZWC6jZVq0aoTgpZoxZsOxVIK+96P7AT0dp/v6ntvzU+s99DkobwiVHYC1ioy 0IQQ== X-Gm-Message-State: AJIora+7h6TnkgVx6gv/rbdh7iO6GR5ulFo07QquB3hoKpU+t9Zg3cFo A0tXp/2wY3QpLby7+T6oy0OLCA== X-Google-Smtp-Source: AGRyM1sZOfFtsIQ40Oun6bhHyx/tTS7MSrkbkGcu1ueGFKWLbKHLeFdMMbXYXrv+4hW9JJWIBtlHWg== X-Received: by 2002:a63:ce13:0:b0:40d:d291:7710 with SMTP id y19-20020a63ce13000000b0040dd2917710mr13573244pgf.269.1658816732987; Mon, 25 Jul 2022 23:25:32 -0700 (PDT) Received: from C02DW0BEMD6R.bytedance.net ([139.177.225.241]) by smtp.gmail.com with ESMTPSA id d11-20020a63d64b000000b00416212f8da7sm9423951pgj.44.2022.07.25.23.25.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Jul 2022 23:25:32 -0700 (PDT) From: Qi Zheng To: akpm@linux-foundation.org, david@redhat.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qi Zheng Subject: [PATCH] mm: fix NULL pointer dereference in wp_page_reuse() Date: Tue, 26 Jul 2022 14:24:36 +0800 Message-Id: <20220726062436.90290-1-zhengqi.arch@bytedance.com> X-Mailer: git-send-email 2.24.3 (Apple Git-128) MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The vmf->page can be NULL when the wp_page_reuse() is invoked by wp_pfn_shared(), it will cause the following panic: [ 12.981200] BUG: kernel NULL pointer dereference, address: 0000000000000= 08 [ 12.981954] #PF: supervisor read access in kernel mode [ 12.982615] #PF: error_code(0x0000) - not-present page [ 12.983146] PGD 0 P4D 0 [ 12.983417] Oops: 0000 [#1] PREEMPT SMP PTI [ 12.983846] CPU: 18 PID: 923 Comm: Xorg Not tainted 5.19.0-rc8.bm.1-amd6= 4 #263 [ 12.984606] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS = rel-1.14.0-0-g14 [ 12.985760] RIP: 0010:_compound_head+0x0/0x40 [...] [ 12.995932] Call Trace: [ 12.996199] [ 12.996424] wp_page_reuse+0x1c/0xa0 [ 12.996800] do_wp_page+0x1a5/0x3f0 [ 12.997169] __handle_mm_fault+0x8cf/0xd20 [ 12.997587] ? _raw_spin_unlock_irqrestore+0x23/0x35 [ 12.998105] handle_mm_fault+0xd5/0x2a0 [ 12.998499] do_user_addr_fault+0x1d0/0x680 [ 12.998930] exc_page_fault+0x78/0x170 [ 12.999321] asm_exc_page_fault+0x22/0x30 To fix it, this patch performs a NULL pointer check before dereferencing the vmf->page. Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with = PG_anon_exclusive") Signed-off-by: Qi Zheng Reviewed-by: David Hildenbrand --- mm/memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index 4cf7d4b6c950..9174918ce3f7 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3043,7 +3043,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf) pte_t entry; =20 VM_BUG_ON(!(vmf->flags & FAULT_FLAG_WRITE)); - VM_BUG_ON(PageAnon(page) && !PageAnonExclusive(page)); + VM_BUG_ON(page && PageAnon(page) && !PageAnonExclusive(page)); =20 /* * Clear the pages cpupid information as the existing --=20 2.20.1