The code in __brd_direct_access multiplies the pgoff variable by page size
and divides it by 512. It can cause overflow on 32-bit architectures. The
overflow happens if we create ramdisk larger than 4G and use it as a
sparse device.
This patch replaces multiplication and division with multiplication by the
number of sectors per page.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Fixes: 1647b9b959c7 ("brd: add dax_operations support")
Cc: stable@xxxxxxxxxxxxxxx # 4.12+
---
drivers/block/brd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Index: linux-4.13/drivers/block/brd.c
===================================================================
--- linux-4.13.orig/drivers/block/brd.c
+++ linux-4.13/drivers/block/brd.c
@@ -339,7 +339,7 @@ static long __brd_direct_access(struct b
if (!brd)
return -ENODEV;
- page = brd_insert_page(brd, PFN_PHYS(pgoff) / 512);
+ page = brd_insert_page(brd, (sector_t)pgoff << PAGE_SECTORS_SHIFT);
if (!page)
return -ENOSPC;
*kaddr = page_address(page);
