From mboxrd@z Thu Jan 1 00:00:00 1970 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 DAC11C74A5B for ; Wed, 22 Mar 2023 14:17:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231262AbjCVORp (ORCPT ); Wed, 22 Mar 2023 10:17:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50330 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229521AbjCVORn (ORCPT ); Wed, 22 Mar 2023 10:17:43 -0400 Received: from mail-wm1-x333.google.com (mail-wm1-x333.google.com [IPv6:2a00:1450:4864:20::333]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 01FF9474FF; Wed, 22 Mar 2023 07:17:41 -0700 (PDT) Received: by mail-wm1-x333.google.com with SMTP id j18-20020a05600c1c1200b003ee5157346cso1805155wms.1; Wed, 22 Mar 2023 07:17:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1679494660; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=cY5q38znnygXEk7MQGfhMNT6fWhXSJdRMwyHM9vnLSQ=; b=dIwol5PJw0bli8FE/ZdtKot7+ZBxkF2CumwPnWIKpYhM02k1csFlwUqD9UGL9WmVLn 3kH6HAxlp3zElAHVcqZypb6dzIguKMqxaZdPSUkRnzfNpZ+N4ajFYn8D3b+VhenoWaBp +nnPFx0qewJW0Z9sGBiil1IqIbwimdDzq+2ZHg5jFcHk4R9l9QrA1w7YDnAlgfbxCbiC L2Vc4UCY2jyTccq0OukQszIqjXzgfCupsM/z8pFZQ9QHNq2a5ZvtpPIZc0orj1WSiBoB rc1D+fk/Dfij3pJZZPenfpqa0GCgLTSnTQgL81J54JFfeZPxhebLOK+xsOuXEpHNlC59 2l8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679494660; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=cY5q38znnygXEk7MQGfhMNT6fWhXSJdRMwyHM9vnLSQ=; b=3SNGDlVgpcXeSyC9d8rYW24Vuiu2YMIewgIebSZjUeknQPlnxMtFRvpap630jkYjc4 QmZipirXJQHqz2de14i3Ndfmku2Ai+u8COeSCjieEY9huCEcbjJ13OwiqjdoIdd1Muiy ol5+13aJKP3Yv8+koVZZIbf1DWNnrUSzMLyaTuKTkeRiRFH30ZlWcH3KeXc64OUZ6uwS HKUv4mq5VjktNoJfILVqhgp5e8w+CCl3J6lCs38f4yaa8aeBIFWrnV/5/xuP7PcziMYk 0R/KkVVPpAb2SUsBGGCefA0gkkkw3VIxDidrgh1vkcuRqee1JAeWUZSzkNTGEm4pDFeb bhWQ== X-Gm-Message-State: AO0yUKUkqJk3QXngQZSVz2b9Tsg5GvQ7wYxha/4gF8i6tMY7wJcAFdxh Wa/F0fFq52B4aQZayZ4X/szymaDoD7Y= X-Google-Smtp-Source: AK7set/t+90cniOBUsMZ86ATkrJz4GVX1skOO3/GxVxqGNazKFn1JFfEJ5wqrdwgjLijJkQ5YI4B9g== X-Received: by 2002:a7b:c00b:0:b0:3ed:2b27:5bcc with SMTP id c11-20020a7bc00b000000b003ed2b275bccmr5684047wmb.38.1679494660074; Wed, 22 Mar 2023 07:17:40 -0700 (PDT) Received: from lucifer.home ([2a00:23c5:dc8c:8701:1663:9a35:5a7b:1d76]) by smtp.googlemail.com with ESMTPSA id h20-20020a1ccc14000000b003dc522dd25esm16824893wmb.30.2023.03.22.07.17.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Mar 2023 07:17:39 -0700 (PDT) From: Lorenzo Stoakes To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton Cc: Baoquan He , Uladzislau Rezki , Matthew Wilcox , David Hildenbrand , Liu Shixin , Jiri Olsa , Jens Axboe , Alexander Viro , Lorenzo Stoakes Subject: [PATCH v5 1/4] fs/proc/kcore: avoid bounce buffer for ktext data Date: Wed, 22 Mar 2023 14:17:32 +0000 Message-Id: X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit df04abfd181a ("fs/proc/kcore.c: Add bounce buffer for ktext data") introduced the use of a bounce buffer to retrieve kernel text data for /proc/kcore in order to avoid failures arising from hardened user copies enabled by CONFIG_HARDENED_USERCOPY in check_kernel_text_object(). We can avoid doing this if instead of copy_to_user() we use _copy_to_user() which bypasses the hardening check. This is more efficient than using a bounce buffer and simplifies the code. We do so as part an overall effort to eliminate bounce buffer usage in the function with an eye to converting it an iterator read. Signed-off-by: Lorenzo Stoakes Reviewed-by: David Hildenbrand --- fs/proc/kcore.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 71157ee35c1a..556f310d6aa4 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -541,19 +541,12 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) case KCORE_VMEMMAP: case KCORE_TEXT: /* - * Using bounce buffer to bypass the - * hardened user copy kernel text checks. + * We use _copy_to_user() to bypass usermode hardening + * which would otherwise prevent this operation. */ - if (copy_from_kernel_nofault(buf, (void *)start, tsz)) { - if (clear_user(buffer, tsz)) { - ret = -EFAULT; - goto out; - } - } else { - if (copy_to_user(buffer, buf, tsz)) { - ret = -EFAULT; - goto out; - } + if (_copy_to_user(buffer, (char *)start, tsz)) { + ret = -EFAULT; + goto out; } break; default: -- 2.39.2 From mboxrd@z Thu Jan 1 00:00:00 1970 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 B4B45C6FD1C for ; Wed, 22 Mar 2023 14:19:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231490AbjCVOTZ (ORCPT ); Wed, 22 Mar 2023 10:19:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53698 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231448AbjCVOTG (ORCPT ); Wed, 22 Mar 2023 10:19:06 -0400 Received: from mail-wm1-x32d.google.com (mail-wm1-x32d.google.com [IPv6:2a00:1450:4864:20::32d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C061A64A88; Wed, 22 Mar 2023 07:19:04 -0700 (PDT) Received: by mail-wm1-x32d.google.com with SMTP id l15-20020a05600c4f0f00b003ed58a9a15eso11602377wmq.5; Wed, 22 Mar 2023 07:19:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1679494743; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=cY5q38znnygXEk7MQGfhMNT6fWhXSJdRMwyHM9vnLSQ=; b=HtWBEQdpIyt5NClQs0GdEyVX0BQhYMynOh3L+SPvjL7xgirih/3eFJWoVgV996pp2F VcWMq3wYNnf2qhxaZ3BRs9EjbhpXfgwyMfxbbnhqyQNU/FRy9P9md93Rk3qN2UsRE+0G c0XyTpZPfGgcVz5nd3+agIrx68G/wVqBh0h7ac744sMSO+20LJn0uGdcSuhBMro0qe1+ VlMqfbspX9JwjjZvXUtw0gOEHFnFTBBrkOEGkfIfZ34qN16vlOQuIl5oXrWHQDr3MtJA UOEm3zuTtt7Z8SX1B/KlpSEfE4v9c7GzzDWiJFWGTHgG1CyxPEqUmLrPTq4x1i+z7Q3z YURg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679494743; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=cY5q38znnygXEk7MQGfhMNT6fWhXSJdRMwyHM9vnLSQ=; b=hBSeLcS+A3Txb0lVmM4XLRBR1JpKtpTZYwf+5PdSh0S73ats51EsIKhq7vBIvlcMIP lhFTT7Stq/67uoDrQwajKNM7ehT2YOq/cneTcXEKQCAciw4E0FMCYIR4pAO/J4mOZmFH kqsk2lsCe1S2N7rrRSZ4/z6d92otiWWq7WGoOv1UbWZT0D8paAZKCbxrncvBcOXRkp0e Z+h1fJ90bzgXfyzZD32AiVLkhXU7gzQKyBRc8nLbjeFBGgN40HDpn8AMC7fyUyv6YULF 6SwgaB8Jzmgdm7dayXE8giRjWbx5Y4DdeqS6/eLSaXcSYxQkhp64VsrRMVlT+Cp6prjs gPGA== X-Gm-Message-State: AO0yUKXAnu6EIaynJqkdt6NmjPjO4X1HEBMgyUDOLS7lLd1bDtd2MhWL +ggGU99Sur/o2SWfwG+SLi4= X-Google-Smtp-Source: AK7set8J49qBttZoi9GR8uqyqgWfN+x1MDD5GFiNt/4HwOkw6Rfvxx4y7uoZSw2RZCb/Jhtr8mW7dA== X-Received: by 2002:a7b:ca57:0:b0:3ee:c06:e942 with SMTP id m23-20020a7bca57000000b003ee0c06e942mr5420804wml.25.1679494742951; Wed, 22 Mar 2023 07:19:02 -0700 (PDT) Received: from lucifer.home ([2a00:23c5:dc8c:8701:1663:9a35:5a7b:1d76]) by smtp.googlemail.com with ESMTPSA id f20-20020a7bcd14000000b003e203681b26sm16872855wmj.29.2023.03.22.07.19.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Mar 2023 07:19:02 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton Cc: Baoquan He , Uladzislau Rezki , Matthew Wilcox , David Hildenbrand , Liu Shixin , Jiri Olsa , Jens Axboe , Alexander Viro , Lorenzo Stoakes Subject: [PATCH v5 1/4] fs/proc/kcore: avoid bounce buffer for ktext data Date: Wed, 22 Mar 2023 14:18:48 +0000 Message-ID: X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Message-ID: <20230322141848.FdGaLpK6Sqq1WlfdMdY1gQbsHjazGDPGnnLrMMoKEbM@z> Commit df04abfd181a ("fs/proc/kcore.c: Add bounce buffer for ktext data") introduced the use of a bounce buffer to retrieve kernel text data for /proc/kcore in order to avoid failures arising from hardened user copies enabled by CONFIG_HARDENED_USERCOPY in check_kernel_text_object(). We can avoid doing this if instead of copy_to_user() we use _copy_to_user() which bypasses the hardening check. This is more efficient than using a bounce buffer and simplifies the code. We do so as part an overall effort to eliminate bounce buffer usage in the function with an eye to converting it an iterator read. Signed-off-by: Lorenzo Stoakes Reviewed-by: David Hildenbrand --- fs/proc/kcore.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 71157ee35c1a..556f310d6aa4 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -541,19 +541,12 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) case KCORE_VMEMMAP: case KCORE_TEXT: /* - * Using bounce buffer to bypass the - * hardened user copy kernel text checks. + * We use _copy_to_user() to bypass usermode hardening + * which would otherwise prevent this operation. */ - if (copy_from_kernel_nofault(buf, (void *)start, tsz)) { - if (clear_user(buffer, tsz)) { - ret = -EFAULT; - goto out; - } - } else { - if (copy_to_user(buffer, buf, tsz)) { - ret = -EFAULT; - goto out; - } + if (_copy_to_user(buffer, (char *)start, tsz)) { + ret = -EFAULT; + goto out; } break; default: -- 2.39.2