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

Message ID 20230202204428.3267832-3-willy@infradead.org
State New
Headers
Series Fix a minor POSIX conformance problem |

Commit Message

Matthew Wilcox Feb. 2, 2023, 8:44 p.m. UTC 
  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@infradead.org>
---
 fs/ext4/inode.c | 1 +
 1 file changed, 1 insertion(+)
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Patch

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);
 			}