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>
---
mm/shmem.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/shmem.c b/mm/shmem.c
index 0005ab2c29af..2c8e8b417b00 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1124,6 +1124,8 @@ static int shmem_setattr(struct user_namespace *mnt_userns,
if (oldsize > holebegin)
unmap_mapping_range(inode->i_mapping,
holebegin, 0, 1);
+ } else {
+ shmem_truncate_range(inode, oldsize, newsize);
}
}
--
2.35.1
