[PATCH 7.2.y 2/2] ntfs: take invalidate_lock in ntfs_setattr_size()

[Sasha Levin <sashal@kernel.org>]

From: Hongling Zeng <zenghongling@kylinos.cn>

[ Upstream commit 9cc5761b8f28f9cef72061094eb5e37e2cd44d97 ]

ntfs_setattr_size() updates i_size and resizes the on-disk attribute
without holding mapping->invalidate_lock.  Page faults take the lock
shared, so a fault racing the resize can resolve a VCN against the
transient runlist state of ntfs_non_resident_attr_expand() and fail
with a spurious SIGBUS, and can interleave with the size-change
epilogue (truncate_pagecache(), i_size_write(),
pagecache_isize_extended()).

Take invalidate_lock exclusively around the whole resize after
inode_dio_wait(), matching the fallocate path and other filesystems
such as xfs, which wraps truncate in its mmaplock (= invalidate_lock).

Fixes: 9c87959601e8 ("ntfs: update file operations")
Cc: stable@vger.kernel.org
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Reviewed-by: Baolin Liu <liubaolin@kylinos.cn>
Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ntfs/file.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index 265f780c1f92d..fb8e525743970 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -269,18 +269,25 @@ static int ntfs_setattr_size(struct inode *vi, struct iattr *attr)
 		return err;
 
 	inode_dio_wait(vi);
+
+	/*
+	 * Serialize with page faults and pagecache instantiation so that
+	 * readers cannot observe the size change until the attribute
+	 * updates below have completed.
+	 */
+	filemap_invalidate_lock(vi->i_mapping);
 	if (attr->ia_size > old_size) {
 		truncate_pagecache(vi, old_size);
 		i_size_write(vi, attr->ia_size);
 		pagecache_isize_extended(vi, old_size, attr->ia_size);
-	} else
+	} else {
 		truncate_setsize(vi, attr->ia_size);
+	}
 
 	err = ntfs_truncate_vfs(vi, attr->ia_size, old_size);
-	if (err) {
+	if (err)
 		i_size_write(vi, old_size);
-		return err;
-	}
+	filemap_invalidate_unlock(vi->i_mapping);
 
 	return err;
 }
-- 
2.53.0