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 AC0D0C43217 for ; Wed, 24 Nov 2021 13:11:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346240AbhKXNOP (ORCPT ); Wed, 24 Nov 2021 08:14:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:53880 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348003AbhKXNMZ (ORCPT ); Wed, 24 Nov 2021 08:12:25 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 183CE6140B; Wed, 24 Nov 2021 12:42:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1637757753; bh=Uf/Wcztr9Wvb/Kimt4by+bdPmpJPrLRDszZo1cXBh24=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=M+3bbNYq2oXtV1HvY9Y3r9ydaK00nTp1lfNiCkeFZr73ygTI2FQ8bU2IabwB2z7w2 mjYTiQXZLebU6nWSKNgv5Z71pcz0r4T9tx22c2GPvXy4zpR0bmfdqo1Mf8NTXm7N3v NYyRQ6fSHeNgw/SX/oN2576Yv4vTKgNCceCp9qBA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Chao Yu , Gao Xiang Subject: [PATCH 4.19 258/323] erofs: fix unsafe pagevec reuse of hooked pclusters Date: Wed, 24 Nov 2021 12:57:28 +0100 Message-Id: <20211124115727.597633999@linuxfoundation.org> X-Mailer: git-send-email 2.34.0 In-Reply-To: <20211124115718.822024889@linuxfoundation.org> References: <20211124115718.822024889@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Gao Xiang commit 86432a6dca9bed79111990851df5756d3eb5f57c upstream. There are pclusters in runtime marked with Z_EROFS_PCLUSTER_TAIL before actual I/O submission. Thus, the decompression chain can be extended if the following pcluster chain hooks such tail pcluster. As the related comment mentioned, if some page is made of a hooked pcluster and another followed pcluster, it can be reused for in-place I/O (since I/O should be submitted anyway): _______________________________________________________________ | tail (partial) page | head (partial) page | |_____PRIMARY_HOOKED___|____________PRIMARY_FOLLOWED____________| However, it's by no means safe to reuse as pagevec since if such PRIMARY_HOOKED pclusters finally move into bypass chain without I/O submission. It's somewhat hard to reproduce with LZ4 and I just found it (general protection fault) by ro_fsstressing a LZMA image for long time. I'm going to actively clean up related code together with multi-page folio adaption in the next few months. Let's address it directly for easier backporting for now. Call trace for reference: z_erofs_decompress_pcluster+0x10a/0x8a0 [erofs] z_erofs_decompress_queue.isra.36+0x3c/0x60 [erofs] z_erofs_runqueue+0x5f3/0x840 [erofs] z_erofs_readahead+0x1e8/0x320 [erofs] read_pages+0x91/0x270 page_cache_ra_unbounded+0x18b/0x240 filemap_get_pages+0x10a/0x5f0 filemap_read+0xa9/0x330 new_sync_read+0x11b/0x1a0 vfs_read+0xf1/0x190 Link: https://lore.kernel.org/r/20211103182006.4040-1-xiang@kernel.org Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support") Cc: # 4.19+ Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Signed-off-by: Greg Kroah-Hartman --- drivers/staging/erofs/unzip_pagevec.h | 13 ++++++++++--- drivers/staging/erofs/unzip_vle.c | 17 +++++++++-------- 2 files changed, 19 insertions(+), 11 deletions(-) --- a/drivers/staging/erofs/unzip_pagevec.h +++ b/drivers/staging/erofs/unzip_pagevec.h @@ -117,11 +117,18 @@ static inline void z_erofs_pagevec_ctor_ static inline bool z_erofs_pagevec_ctor_enqueue(struct z_erofs_pagevec_ctor *ctor, struct page *page, - enum z_erofs_page_type type) + enum z_erofs_page_type type, + bool pvec_safereuse) { - if (unlikely(ctor->next == NULL && type)) - if (ctor->index + 1 == ctor->nr) + if (!ctor->next) { + /* some pages cannot be reused as pvec safely without I/O */ + if (type == Z_EROFS_PAGE_TYPE_EXCLUSIVE && !pvec_safereuse) + type = Z_EROFS_VLE_PAGE_TYPE_TAIL_SHARED; + + if (type != Z_EROFS_PAGE_TYPE_EXCLUSIVE && + ctor->index + 1 == ctor->nr) return false; + } if (unlikely(ctor->index >= ctor->nr)) z_erofs_pagevec_ctor_pagedown(ctor, false); --- a/drivers/staging/erofs/unzip_vle.c +++ b/drivers/staging/erofs/unzip_vle.c @@ -228,10 +228,10 @@ static inline bool try_to_reuse_as_compr } /* callers must be with work->lock held */ -static int z_erofs_vle_work_add_page( - struct z_erofs_vle_work_builder *builder, - struct page *page, - enum z_erofs_page_type type) +static int z_erofs_vle_work_add_page(struct z_erofs_vle_work_builder *builder, + struct page *page, + enum z_erofs_page_type type, + bool pvec_safereuse) { int ret; @@ -241,9 +241,9 @@ static int z_erofs_vle_work_add_page( try_to_reuse_as_compressed_page(builder, page)) return 0; - ret = z_erofs_pagevec_ctor_enqueue(&builder->vector, page, type); + ret = z_erofs_pagevec_ctor_enqueue(&builder->vector, page, type, + pvec_safereuse); builder->work->vcnt += (unsigned)ret; - return ret ? 0 : -EAGAIN; } @@ -688,14 +688,15 @@ hitted: tight &= builder_is_followed(builder); retry: - err = z_erofs_vle_work_add_page(builder, page, page_type); + err = z_erofs_vle_work_add_page(builder, page, page_type, + builder_is_followed(builder)); /* should allocate an additional staging page for pagevec */ if (err == -EAGAIN) { struct page *const newpage = __stagingpage_alloc(page_pool, GFP_NOFS); err = z_erofs_vle_work_add_page(builder, - newpage, Z_EROFS_PAGE_TYPE_EXCLUSIVE); + newpage, Z_EROFS_PAGE_TYPE_EXCLUSIVE, true); if (likely(!err)) goto retry; }