From nobody Sun Feb 8 02:21:41 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 E6F3DC04A94 for ; Mon, 31 Jul 2023 21:51:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231624AbjGaVvB (ORCPT ); Mon, 31 Jul 2023 17:51:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58570 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231504AbjGaVu4 (ORCPT ); Mon, 31 Jul 2023 17:50:56 -0400 Received: from mail-wm1-x336.google.com (mail-wm1-x336.google.com [IPv6:2a00:1450:4864:20::336]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 80589E7; Mon, 31 Jul 2023 14:50:33 -0700 (PDT) Received: by mail-wm1-x336.google.com with SMTP id 5b1f17b1804b1-3fbc5d5742eso54961405e9.3; Mon, 31 Jul 2023 14:50:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1690840232; x=1691445032; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=LzzSGKWkmVAwS6+5gn2kW/zuOpGQRDh54S2FzorJoyA=; b=Gh6QtEjOYwj9odnsjh1f9DapsMkYw7zBcT5m9Kd1gaN0YupuuaRA1tt+K3+L1M0cAN +iRFN3msBWUF/UKb2JDD+6GJI2Gv1MpevVryLb9Bdoci+QBKe5pT1Wnv8UJK1ofVufOb xeETko2BcN4dMLmlLu7ea6ABxmGItWChPuqDD1x9cUqb5NUk/8kVlI50gFWAC4FIgthg WykjFjx6566tCwyrYocar6zjVxbZ7lNyX5ar+4lNWJQ7d9yEO/PAgOrNAibQMW6T2vPX 2q5ZT1t0X6cQnwloXqZRTBwwiJ4F+bpq6IzkWzbzTq3MGZKXR6b1Dil1dLPiW+t7xm03 L/Dg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690840232; x=1691445032; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=LzzSGKWkmVAwS6+5gn2kW/zuOpGQRDh54S2FzorJoyA=; b=E957p7m1n4ECUvhYapME1VVCeave8eJhoB0ZmhLlngqp/d5fX4WbMjwi4DinVxWuZv LSa5LhRrJFgx0rdcbmPYNDAUw6GJCccOUAXQRpc1IOwircYR/pBwvNzAWPLUUp0/anHf iZxmHMCgk/MjOp2+3gHyQ5CCMOcZC86ckIJhtCN1NK915JvqdQRwsFciOn4fldL2mh19 moRqyQAuBwUc3rTW6jGtrfq6Wzd9vWBt9tIufi8BHt2Rvxi4qp+jsauLGaTqEEJYaFKj qH6ehPMepF4U2+ff2jGvCWc75RmZId4z+4y+khJcZXKN2tAFd1SKRu7Dnwg2Qj3UMwPE mn2g== X-Gm-Message-State: ABy/qLaO/GaqZypvHCNgazW7dDBf9AVm2ow/U4iQwVlcRQZr2UiiWONO vde3TKXKqLfyGM9qpb1X/ywBuAeQ+Ds= X-Google-Smtp-Source: APBJJlGkZeJD/ErBNLIHuV84FQDDzVLXS/9Ndpi2HOQ7+mZlSHPebNAIlPGdzhNi1ilsx784crY0JQ== X-Received: by 2002:a7b:cd1a:0:b0:3fc:92:73d6 with SMTP id f26-20020a7bcd1a000000b003fc009273d6mr854436wmj.11.1690840231335; Mon, 31 Jul 2023 14:50:31 -0700 (PDT) Received: from lucifer.home ([2a00:23c5:dc8c:8701:1663:9a35:5a7b:1d76]) by smtp.googlemail.com with ESMTPSA id d12-20020a1c730c000000b003fa999cefc0sm12123626wmb.36.2023.07.31.14.50.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Jul 2023 14:50:30 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Cc: Baoquan He , Uladzislau Rezki , linux-fsdevel@vger.kernel.org, Jiri Olsa , Will Deacon , Mike Galbraith , Mark Rutland , wangkefeng.wang@huawei.com, catalin.marinas@arm.com, ardb@kernel.org, David Hildenbrand , Linux regression tracking , regressions@lists.linux.dev, Matthew Wilcox , Liu Shixin , Jens Axboe , Alexander Viro , Lorenzo Stoakes , stable@vger.kernel.org Subject: [PATCH] fs/proc/kcore: reinstate bounce buffer for KCORE_TEXT regions Date: Mon, 31 Jul 2023 22:50:21 +0100 Message-ID: <20230731215021.70911-1-lstoakes@gmail.com> X-Mailer: git-send-email 2.41.0 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" Some architectures do not populate the entire range categorised by KCORE_TEXT, so we must ensure that the kernel address we read from is valid. Unfortunately there is no solution currently available to do so with a purely iterator solution so reinstate the bounce buffer in this instance so we can use copy_from_kernel_nofault() in order to avoid page faults when regions are unmapped. This change partly reverts commit 2e1c0170771e ("fs/proc/kcore: avoid bounce buffer for ktext data"), reinstating the bounce buffer, but adapts the code to continue to use an iterator. Fixes: 2e1c0170771e ("fs/proc/kcore: avoid bounce buffer for ktext data") Reported-by: Jiri Olsa Closes: https://lore.kernel.org/all/ZHc2fm+9daF6cgCE@krava Cc: stable@vger.kernel.org Signed-off-by: Lorenzo Stoakes Acked-by: David Hildenbrand Reviewed-by: Baoquan He Tested-by: Baoquan He Tested-by: Jiri Olsa Tested-by: Will Deacon --- fs/proc/kcore.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 9cb32e1a78a0..3bc689038232 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -309,6 +309,8 @@ static void append_kcore_note(char *notes, size_t *i, c= onst char *name, =20 static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter) { + struct file *file =3D iocb->ki_filp; + char *buf =3D file->private_data; loff_t *fpos =3D &iocb->ki_pos; size_t phdrs_offset, notes_offset, data_offset; size_t page_offline_frozen =3D 1; @@ -554,11 +556,22 @@ static ssize_t read_kcore_iter(struct kiocb *iocb, st= ruct iov_iter *iter) fallthrough; case KCORE_VMEMMAP: case KCORE_TEXT: + /* + * Sadly we must use a bounce buffer here to be able to + * make use of copy_from_kernel_nofault(), as these + * memory regions might not always be mapped on all + * architectures. + */ + if (copy_from_kernel_nofault(buf, (void *)start, tsz)) { + if (iov_iter_zero(tsz, iter) !=3D tsz) { + ret =3D -EFAULT; + goto out; + } /* * We use _copy_to_iter() to bypass usermode hardening * which would otherwise prevent this operation. */ - if (_copy_to_iter((char *)start, tsz, iter) !=3D tsz) { + } else if (_copy_to_iter(buf, tsz, iter) !=3D tsz) { ret =3D -EFAULT; goto out; } @@ -595,6 +608,10 @@ static int open_kcore(struct inode *inode, struct file= *filp) if (ret) return ret; =20 + filp->private_data =3D kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!filp->private_data) + return -ENOMEM; + if (kcore_need_update) kcore_update_ram(); if (i_size_read(inode) !=3D proc_root_kcore->size) { @@ -605,9 +622,16 @@ static int open_kcore(struct inode *inode, struct file= *filp) return 0; } =20 +static int release_kcore(struct inode *inode, struct file *file) +{ + kfree(file->private_data); + return 0; +} + static const struct proc_ops kcore_proc_ops =3D { .proc_read_iter =3D read_kcore_iter, .proc_open =3D open_kcore, + .proc_release =3D release_kcore, .proc_lseek =3D default_llseek, }; =20 --=20 2.41.0