From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ipmail03.adl6.internode.on.net ([150.101.137.143]:34563 "EHLO ipmail03.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725898AbeKTHnT (ORCPT ); Tue, 20 Nov 2018 02:43:19 -0500 From: Dave Chinner To: linux-xfs@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Subject: [PATCH 2/5] iomap: sub-block dio needs to zeroout beyond EOF Date: Tue, 20 Nov 2018 08:17:39 +1100 Message-Id: <20181119211742.8824-3-david@fromorbit.com> In-Reply-To: <20181119211742.8824-1-david@fromorbit.com> References: <20181119211742.8824-1-david@fromorbit.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: From: Dave Chinner If we are soing sub-block dio that extends EOF, we need to zero the unused tail of the block to initialise the data in it it. If we do not zero the tail of the block, then an immediate mmap read of the EOF block will expose stale data beyond EOF to userspace. Found with fsx running sub-block DIO sizes vs MAPREAD/MAPWRITE operations. Fix this by detecting if the end of the DIO write is beyond EOF and zeroing the tail if necessary. Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig --- fs/iomap.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/iomap.c b/fs/iomap.c index 72f3864a2e6b..77c214194edf 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -1677,7 +1677,14 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, dio->submit.cookie = submit_bio(bio); } while (nr_pages); - if (need_zeroout) { + /* + * We need to zeroout the tail of a sub-block write if the extent type + * requires zeroing or the write extends beyond EOF. If we don't zero + * the block tail in the latter case, we can expose stale data via mmap + * reads of the EOF block. + */ + if (need_zeroout || + ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) { /* zero out from the end of the write to the end of the block */ pad = pos & (fs_block_size - 1); if (pad) -- 2.19.1