[PATCH 4.9 076/117] 9P: Cast to loff_t before multiplying

[Greg Kroah-Hartman]

From: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>

commit f5f7ab168b9a60e12a4b8f2bb6fcc91321dc23c1 upstream.

On 32-bit systems, this multiplication will overflow for files larger
than 4GB.

Link: http://lkml.kernel.org/r/20201004180428.14494-2-willy@xxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: fb89b45cdfdc ("9P: introduction of a new cache=mmap model.")
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Dominique Martinet <asmadeus@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/9p/vfs_file.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -624,9 +624,9 @@ static void v9fs_mmap_vm_close(struct vm
 	struct writeback_control wbc = {
 		.nr_to_write = LONG_MAX,
 		.sync_mode = WB_SYNC_ALL,
-		.range_start = vma->vm_pgoff * PAGE_SIZE,
+		.range_start = (loff_t)vma->vm_pgoff * PAGE_SIZE,
 		 /* absolute end, byte at end included */
-		.range_end = vma->vm_pgoff * PAGE_SIZE +
+		.range_end = (loff_t)vma->vm_pgoff * PAGE_SIZE +
 			(vma->vm_end - vma->vm_start - 1),
 	};