From: Jan Kara Subject: [PATCH] ext3: Fix data / filesystem corruption when write fails to copy data Date: Mon, 14 Dec 2009 21:35:57 +0100 Message-ID: <1260822957-808-1-git-send-email-jack@suse.cz> Cc: linux-ext4@vger.kernel.org, Jan Kara To: stable@kernel.org Return-path: Received: from cantor2.suse.de ([195.135.220.15]:58684 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751984AbZLNUgG (ORCPT ); Mon, 14 Dec 2009 15:36:06 -0500 Sender: linux-ext4-owner@vger.kernel.org List-ID: When ext3_write_begin fails after allocating some blocks or generic_perform_write fails to copy data to write, we truncate blocks already instantiated beyond i_size. Although these blocks were never inside i_size, we have to truncate pagecache of these blocks so that corresponding buffers get unmapped. Otherwise subsequent __block_prepare_write (called because we are retrying the write) will find the buffers mapped, not call ->get_block, and thus the page will be backed by already freed blocks leading to filesystem and data corruption. Reported-by: James Y Knight Signed-off-by: Jan Kara --- fs/ext3/inode.c | 18 ++++++++++++++---- 1 files changed, 14 insertions(+), 4 deletions(-) The bug has been introduced by commit 9eaaa2d5759837402ec5eee13b2a97921808c3eb and thus this fix needs to be applied to 2.6.31 and 2.6.32 kernels. Currently, it's in Linus's tree as commit 68eb3db08344286733adac48304d9fb7a0e53b27. diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c index 354ed3b..f9d6937 100644 --- a/fs/ext3/inode.c +++ b/fs/ext3/inode.c @@ -1151,6 +1151,16 @@ static int do_journal_get_write_access(handle_t *handle, return ext3_journal_get_write_access(handle, bh); } +/* + * Truncate blocks that were not used by write. We have to truncate the + * pagecache as well so that corresponding buffers get properly unmapped. + */ +static void ext3_truncate_failed_write(struct inode *inode) +{ + truncate_inode_pages(inode->i_mapping, inode->i_size); + ext3_truncate(inode); +} + static int ext3_write_begin(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned flags, struct page **pagep, void **fsdata) @@ -1209,7 +1219,7 @@ write_begin_failed: unlock_page(page); page_cache_release(page); if (pos + len > inode->i_size) - ext3_truncate(inode); + ext3_truncate_failed_write(inode); } if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries)) goto retry; @@ -1304,7 +1314,7 @@ static int ext3_ordered_write_end(struct file *file, page_cache_release(page); if (pos + len > inode->i_size) - ext3_truncate(inode); + ext3_truncate_failed_write(inode); return ret ? ret : copied; } @@ -1330,7 +1340,7 @@ static int ext3_writeback_write_end(struct file *file, page_cache_release(page); if (pos + len > inode->i_size) - ext3_truncate(inode); + ext3_truncate_failed_write(inode); return ret ? ret : copied; } @@ -1383,7 +1393,7 @@ static int ext3_journalled_write_end(struct file *file, page_cache_release(page); if (pos + len > inode->i_size) - ext3_truncate(inode); + ext3_truncate_failed_write(inode); return ret ? ret : copied; } -- 1.6.4.2