[PATCH 3.18 20/29] userns; Correct the comment in map_write

From: Greg Kroah-Hartman
Date: Fri Sep 07 2018 - 17:48:55 EST


3.18-stable review patch. If anyone has any objections, please let me know.

------------------

From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>

commit 36476beac4f8ca9dc7722790b2e8ef0e8e51034e upstream.

It is important that all maps are less than PAGE_SIZE
or else setting the last byte of the buffer to '0'
could write off the end of the allocated storage.

Correct the misleading comment.

Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
kernel/user_namespace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -643,7 +643,7 @@ static ssize_t map_write(struct file *fi
if (!page)
goto out;

- /* Only allow <= page size writes at the beginning of the file */
+ /* Only allow < page size writes at the beginning of the file */
ret = -EINVAL;
if ((*ppos != 0) || (count >= PAGE_SIZE))
goto out;