Ocfs2 devel - Oct 2020 - [PATCH 1/7] 9P: Cast to loff_t before multiplying

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

Cc: stable at vger.kernel.org
Fixes: fb89b45cdfdc ("9P: introduction of a new cache=mmap model.")
Signed-off-by: Matthew Wilcox (Oracle) <willy at infradead.org>
---
 fs/9p/vfs_file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 3576123d8299..6d97b6b4d34b 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -612,9 +612,9 @@ static void v9fs_mmap_vm_close(struct vm_area_struct *vma)
 	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),
 	};
 
-- 
2.28.0

On Sun, Oct 04, 2020 at 07:04:22PM +0100, Matthew Wilcox (Oracle)
wrote:
> On 32-bit systems, this multiplication will overflow for files larger
> than 4GB.
> 
> Cc: stable at vger.kernel.org
> Fixes: fb89b45cdfdc ("9P: introduction of a new cache=mmap
model.")
> Signed-off-by: Matthew Wilcox (Oracle) <willy at infradead.org>
> ---
>  fs/9p/vfs_file.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
> index 3576123d8299..6d97b6b4d34b 100644
> --- a/fs/9p/vfs_file.c
> +++ b/fs/9p/vfs_file.c
> @@ -612,9 +612,9 @@ static void v9fs_mmap_vm_close(struct vm_area_struct
*vma)
>  	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,
Given the may places where this issue shows up I think we really need
a vma_offset or similar helper for it.  Much better than chasing missing
casts everywhere.