From: Eryu Guan <guaneryu@gmail.com>
Date: Thu, 22 Mar 2018 15:41:25 +0000 (-0400)
Subject: ext4: protect i_disksize update by i_data_sem in direct write path
X-Git-Tag: v4.1.12-124.31.3~327
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=c098051d90e95c655ac2367ee935c2816006d692;p=users%2Fjedix%2Flinux-maple.git

ext4: protect i_disksize update by i_data_sem in direct write path

i_disksize update should be protected by i_data_sem, by either taking
the lock explicitly or by using ext4_update_i_disksize() helper. But the
i_disksize updates in ext4_direct_IO_write() are not protected at all,
which may be racing with i_disksize updates in writeback path in
delalloc buffer write path.

This is found by code inspection, and I didn't hit any i_disksize
corruption due to this bug. Thanks to Jan Kara for catching this bug and
suggesting the fix!

Reported-by: Jan Kara <jack@suse.cz>
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

Orabug: 28940828

commit 73fdad00b208b139cf43f3163fbc0f67e4c6047c upstream

Signed-off-by: Brian Maly <brian.maly@oracle.com>

Conflicts:
	fs/ext4/indirect.c
	code line mismatch

Signed-off-by: Shan Hai <shan.hai@oracle.com>
Reviewed-by: Ashish Samant <ashish.samant@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
---

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index e862df31ddda..f5d37de17558 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -647,7 +647,6 @@ ssize_t ext4_ind_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
-	struct ext4_inode_info *ei = EXT4_I(inode);
 	handle_t *handle;
 	ssize_t ret;
 	int orphan = 0;
@@ -670,7 +669,7 @@ ssize_t ext4_ind_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 				goto out;
 			}
 			orphan = 1;
-			ei->i_disksize = inode->i_size;
+			ext4_update_i_disksize(inode, inode->i_size);
 			ext4_journal_stop(handle);
 		}
 	}
@@ -738,7 +737,7 @@ locked:
 		if (ret > 0) {
 			loff_t end = offset + ret;
 			if (end > inode->i_size) {
-				ei->i_disksize = end;
+				ext4_update_i_disksize(inode, end);
 				i_size_write(inode, end);
 				/*
 				 * We're going to return a positive `ret'