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@xxxxxxxxxxxxxxx
> Fixes: fb89b45cdfdc ("9P: introduction of a new cache=mmap model.")
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> ---
> 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.
