From patchwork Wed Jan 20 16:06:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 1429301 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4DLVnP4tD7z9sVm for ; Thu, 21 Jan 2021 03:08:41 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731806AbhATQIJ (ORCPT ); Wed, 20 Jan 2021 11:08:09 -0500 Received: from mx2.suse.de ([195.135.220.15]:42854 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391399AbhATQHB (ORCPT ); Wed, 20 Jan 2021 11:07:01 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id EA3A0AC7B; Wed, 20 Jan 2021 16:06:18 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id ADEC41E07FD; Wed, 20 Jan 2021 17:06:18 +0100 (CET) From: Jan Kara To: Cc: Matthew Wilcox , , Jan Kara Subject: [PATCH 1/3] mm: Do not pass iter into generic_file_buffered_read_get_pages() Date: Wed, 20 Jan 2021 17:06:09 +0100 Message-Id: <20210120160611.26853-2-jack@suse.cz> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210120160611.26853-1-jack@suse.cz> References: <20210120160611.26853-1-jack@suse.cz> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org generic_file_buffered_read_get_pages() needs to only know the length we want to read and whether partially uptodate pages are accepted. Also principially this function just loads pages into page cache so it does not need to know about user buffers to copy data to. Pass the length and whether partially uptodate pages are acceptable into generic_file_buffered_read_get_pages() instead of iter. Signed-off-by: Jan Kara --- mm/filemap.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 5c9d564317a5..7029bada8e90 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2235,7 +2235,7 @@ generic_file_buffered_read_readpage(struct kiocb *iocb, static struct page * generic_file_buffered_read_pagenotuptodate(struct kiocb *iocb, struct file *filp, - struct iov_iter *iter, + bool partial_page, struct page *page, loff_t pos, loff_t count) { @@ -2264,8 +2264,8 @@ generic_file_buffered_read_pagenotuptodate(struct kiocb *iocb, if (inode->i_blkbits == PAGE_SHIFT || !mapping->a_ops->is_partially_uptodate) goto page_not_up_to_date; - /* pipes can't handle partially uptodate pages */ - if (unlikely(iov_iter_is_pipe(iter))) + /* Some reads (e.g. pipes) don't accept partially uptodate pages */ + if (unlikely(!partial_page)) goto page_not_up_to_date; if (!trylock_page(page)) goto page_not_up_to_date; @@ -2304,8 +2304,7 @@ generic_file_buffered_read_pagenotuptodate(struct kiocb *iocb, } static struct page * -generic_file_buffered_read_no_cached_page(struct kiocb *iocb, - struct iov_iter *iter) +generic_file_buffered_read_no_cached_page(struct kiocb *iocb) { struct file *filp = iocb->ki_filp; struct address_space *mapping = filp->f_mapping; @@ -2335,7 +2334,7 @@ generic_file_buffered_read_no_cached_page(struct kiocb *iocb, } static int generic_file_buffered_read_get_pages(struct kiocb *iocb, - struct iov_iter *iter, + size_t len, bool partial_page, struct page **pages, unsigned int nr) { @@ -2343,7 +2342,7 @@ static int generic_file_buffered_read_get_pages(struct kiocb *iocb, struct address_space *mapping = filp->f_mapping; struct file_ra_state *ra = &filp->f_ra; pgoff_t index = iocb->ki_pos >> PAGE_SHIFT; - pgoff_t last_index = (iocb->ki_pos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT; + pgoff_t last_index = (iocb->ki_pos + len + PAGE_SIZE - 1) >> PAGE_SHIFT; int i, j, nr_got, err = 0; nr = min_t(unsigned long, last_index - index, nr); @@ -2364,7 +2363,7 @@ static int generic_file_buffered_read_get_pages(struct kiocb *iocb, if (nr_got) goto got_pages; - pages[0] = generic_file_buffered_read_no_cached_page(iocb, iter); + pages[0] = generic_file_buffered_read_no_cached_page(iocb); err = PTR_ERR_OR_ZERO(pages[0]); if (!IS_ERR_OR_NULL(pages[0])) nr_got = 1; @@ -2374,7 +2373,7 @@ static int generic_file_buffered_read_get_pages(struct kiocb *iocb, pgoff_t pg_index = index + i; loff_t pg_pos = max(iocb->ki_pos, (loff_t) pg_index << PAGE_SHIFT); - loff_t pg_count = iocb->ki_pos + iter->count - pg_pos; + loff_t pg_count = iocb->ki_pos + len - pg_pos; if (PageReadahead(page)) { if (iocb->ki_flags & IOCB_NOIO) { @@ -2399,7 +2398,8 @@ static int generic_file_buffered_read_get_pages(struct kiocb *iocb, } page = generic_file_buffered_read_pagenotuptodate(iocb, - filp, iter, page, pg_pos, pg_count); + filp, partial_page, page, pg_pos, + pg_count); if (IS_ERR_OR_NULL(page)) { for (j = i + 1; j < nr_got; j++) put_page(pages[j]); @@ -2478,8 +2478,8 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb, iocb->ki_flags |= IOCB_NOWAIT; i = 0; - pg_nr = generic_file_buffered_read_get_pages(iocb, iter, - pages, nr_pages); + pg_nr = generic_file_buffered_read_get_pages(iocb, iter->count, + !iov_iter_is_pipe(iter), pages, nr_pages); if (pg_nr < 0) { error = pg_nr; break; From patchwork Wed Jan 20 16:06:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 1429302 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4DLVpX2Pcdz9sVS for ; Thu, 21 Jan 2021 03:09:40 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403770AbhATQIK (ORCPT ); Wed, 20 Jan 2021 11:08:10 -0500 Received: from mx2.suse.de ([195.135.220.15]:42852 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391398AbhATQHB (ORCPT ); Wed, 20 Jan 2021 11:07:01 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id EA4F7AC85; Wed, 20 Jan 2021 16:06:18 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B0A311E082A; Wed, 20 Jan 2021 17:06:18 +0100 (CET) From: Jan Kara To: Cc: Matthew Wilcox , , Jan Kara Subject: [PATCH 2/3] mm: Provide address_space operation for filling pages for read Date: Wed, 20 Jan 2021 17:06:10 +0100 Message-Id: <20210120160611.26853-3-jack@suse.cz> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210120160611.26853-1-jack@suse.cz> References: <20210120160611.26853-1-jack@suse.cz> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Provide an address_space operation for filling pages needed for read into page cache. Filesystems can use this operation to seriealize page cache filling with e.g. hole punching properly. Signed-off-by: Jan Kara --- include/linux/fs.h | 5 +++++ mm/filemap.c | 32 ++++++++++++++++++++++++++------ 2 files changed, 31 insertions(+), 6 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index fd47deea7c17..1d3f963d0d99 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -381,6 +381,9 @@ struct address_space_operations { int (*readpages)(struct file *filp, struct address_space *mapping, struct list_head *pages, unsigned nr_pages); void (*readahead)(struct readahead_control *); + /* Fill in uptodate pages for kiocb into page cache and pagep array */ + int (*fill_pages)(struct kiocb *, size_t len, bool partial_page, + struct page **pagep, unsigned int nr_pages); int (*write_begin)(struct file *, struct address_space *mapping, loff_t pos, unsigned len, unsigned flags, @@ -2962,6 +2965,8 @@ extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *); extern int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count); extern int generic_file_rw_checks(struct file *file_in, struct file *file_out); +extern int generic_file_buffered_read_get_pages(struct kiocb *iocb, size_t len, + bool partial_page, struct page **pages, unsigned int nr); extern ssize_t generic_file_buffered_read(struct kiocb *iocb, struct iov_iter *to, ssize_t already_read); extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *); diff --git a/mm/filemap.c b/mm/filemap.c index 7029bada8e90..5b594dd245e0 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2333,10 +2333,24 @@ generic_file_buffered_read_no_cached_page(struct kiocb *iocb) return generic_file_buffered_read_readpage(iocb, filp, mapping, page); } -static int generic_file_buffered_read_get_pages(struct kiocb *iocb, - size_t len, bool partial_page, - struct page **pages, - unsigned int nr) +/** + * generic_file_buffered_read_get_pages - generic routine to fill in page cache + * pages for a read + * @iocb: the iocb to read + * @len: number of bytes to read + * @partial_page: are partially uptodate pages accepted by read? + * @pages: array where to fill in found pages + * @nr: number of pages in the @pages array + * + * Fill pages into page cache and @pages array needed for a read of length @len + * described by @iocb. + * + * Return: + * Number of pages filled in the array + */ +int generic_file_buffered_read_get_pages(struct kiocb *iocb, size_t len, + bool partial_page, + struct page **pages, unsigned int nr) { struct file *filp = iocb->ki_filp; struct address_space *mapping = filp->f_mapping; @@ -2419,6 +2433,7 @@ static int generic_file_buffered_read_get_pages(struct kiocb *iocb, */ goto find_page; } +EXPORT_SYMBOL(generic_file_buffered_read_get_pages); /** * generic_file_buffered_read - generic file read routine @@ -2447,6 +2462,8 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb, unsigned int nr_pages = min_t(unsigned int, 512, ((iocb->ki_pos + iter->count + PAGE_SIZE - 1) >> PAGE_SHIFT) - (iocb->ki_pos >> PAGE_SHIFT)); + int (*fill_pages)(struct kiocb *, size_t, bool, struct page **, + unsigned int) = mapping->a_ops->fill_pages; int i, pg_nr, error = 0; bool writably_mapped; loff_t isize, end_offset; @@ -2456,6 +2473,9 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb, if (unlikely(!iov_iter_count(iter))) return 0; + if (!fill_pages) + fill_pages = generic_file_buffered_read_get_pages; + iov_iter_truncate(iter, inode->i_sb->s_maxbytes); if (nr_pages > ARRAY_SIZE(pages_onstack)) @@ -2478,8 +2498,8 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb, iocb->ki_flags |= IOCB_NOWAIT; i = 0; - pg_nr = generic_file_buffered_read_get_pages(iocb, iter->count, - !iov_iter_is_pipe(iter), pages, nr_pages); + pg_nr = fill_pages(iocb, iter->count, !iov_iter_is_pipe(iter), + pages, nr_pages); if (pg_nr < 0) { error = pg_nr; break; From patchwork Wed Jan 20 16:06:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 1429300 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4DLVnP1cNrz9sVX for ; Thu, 21 Jan 2021 03:08:41 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390295AbhATQHv (ORCPT ); Wed, 20 Jan 2021 11:07:51 -0500 Received: from mx2.suse.de ([195.135.220.15]:42856 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391401AbhATQHA (ORCPT ); Wed, 20 Jan 2021 11:07:00 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id EBD0DAF32; Wed, 20 Jan 2021 16:06:18 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B4D381E0831; Wed, 20 Jan 2021 17:06:18 +0100 (CET) From: Jan Kara To: Cc: Matthew Wilcox , , Jan Kara , stable@vger.kernel.org, Amir Goldstein Subject: [PATCH 3/3] ext4: Fix stale data exposure when read races with hole punch Date: Wed, 20 Jan 2021 17:06:11 +0100 Message-Id: <20210120160611.26853-4-jack@suse.cz> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210120160611.26853-1-jack@suse.cz> References: <20210120160611.26853-1-jack@suse.cz> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Hole puching currently evicts pages from page cache and then goes on to remove blocks from the inode. This happens under both i_mmap_sem and i_rwsem held exclusively which provides appropriate serialization with racing page faults. However there is currently nothing that prevents ordinary read(2) from racing with the hole punch and instantiating page cache page after hole punching has evicted page cache but before it has removed blocks from the inode. This page cache page will be mapping soon to be freed block and that can lead to returning stale data to userspace or even filesystem corruption. Fix the problem by protecting reads as well as readahead requests with i_mmap_sem. CC: stable@vger.kernel.org Reported-by: Amir Goldstein Signed-off-by: Jan Kara --- fs/ext4/file.c | 16 ++++++++++++++++ fs/ext4/inode.c | 21 +++++++++++++++++++++ 2 files changed, 37 insertions(+) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 349b27f0dda0..d66f7c08b123 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -30,6 +30,7 @@ #include #include #include +#include #include "ext4.h" #include "ext4_jbd2.h" #include "xattr.h" @@ -131,6 +132,20 @@ static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to) return generic_file_read_iter(iocb, to); } +static int ext4_fadvise(struct file *filp, loff_t start, loff_t end, int advice) +{ + struct inode *inode = file_inode(filp); + int ret; + + /* Readahead needs protection from hole punching and similar ops */ + if (advice == POSIX_FADV_WILLNEED) + down_read(&EXT4_I(inode)->i_mmap_sem); + ret = generic_fadvise(filp, start, end, advice); + if (advice == POSIX_FADV_WILLNEED) + up_read(&EXT4_I(inode)->i_mmap_sem); + return ret; +} + /* * Called when an inode is released. Note that this is different * from ext4_file_open: open gets called at every open, but release @@ -911,6 +926,7 @@ const struct file_operations ext4_file_operations = { .splice_read = generic_file_splice_read, .splice_write = iter_file_splice_write, .fallocate = ext4_fallocate, + .fadvise = ext4_fadvise, }; const struct inode_operations ext4_file_inode_operations = { diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index c173c8405856..a01569f2fa49 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3646,9 +3646,28 @@ static int ext4_iomap_swap_activate(struct swap_info_struct *sis, &ext4_iomap_report_ops); } +static int ext4_fill_pages(struct kiocb *iocb, size_t len, bool partial_page, + struct page **pagep, unsigned int nr_pages) +{ + struct ext4_inode_info *ei = EXT4_I(iocb->ki_filp->f_mapping->host); + int ret; + + /* + * Protect adding of pages into page cache against hole punching and + * other cache manipulation functions so that we don't expose + * potentially stale user data. + */ + down_read(&ei->i_mmap_sem); + ret = generic_file_buffered_read_get_pages(iocb, len, partial_page, + pagep, nr_pages); + up_read(&ei->i_mmap_sem); + return ret; +} + static const struct address_space_operations ext4_aops = { .readpage = ext4_readpage, .readahead = ext4_readahead, + .fill_pages = ext4_fill_pages, .writepage = ext4_writepage, .writepages = ext4_writepages, .write_begin = ext4_write_begin, @@ -3667,6 +3686,7 @@ static const struct address_space_operations ext4_aops = { static const struct address_space_operations ext4_journalled_aops = { .readpage = ext4_readpage, .readahead = ext4_readahead, + .fill_pages = ext4_fill_pages, .writepage = ext4_writepage, .writepages = ext4_writepages, .write_begin = ext4_write_begin, @@ -3684,6 +3704,7 @@ static const struct address_space_operations ext4_journalled_aops = { static const struct address_space_operations ext4_da_aops = { .readpage = ext4_readpage, .readahead = ext4_readahead, + .fill_pages = ext4_fill_pages, .writepage = ext4_writepage, .writepages = ext4_writepages, .write_begin = ext4_da_write_begin,