[PATCH 2/5] ext4: Zero bytes after 'oldsize' if we're expanding the file

[Matthew Wilcox (Oracle)]

POSIX requires that "If the file size is increased, the extended area
shall appear as if it were zero-filled".  It is possible to use mmap to
write past EOF and that data will become visible instead of zeroes.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 fs/ext4/inode.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9d9f414f99fe..14e3fa99f733 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5604,6 +5604,7 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 			if (!shrink) {
 				pagecache_isize_extended(inode, oldsize,
 							 inode->i_size);
+				truncate_pagecache(inode, oldsize);
 			} else if (ext4_should_journal_data(inode)) {
 				ext4_wait_for_tail_page_commit(inode);
 			}
-- 
2.35.1