Messages in this thread Patch in this message | | | Date | Wed, 13 Sep 2017 09:17:57 -0400 (EDT) | From | Mikulas Patocka <> | Subject | [PATCH] brd: fix overflow in __brd_direct_access |
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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@redhat.com> Fixes: 1647b9b959c7 ("brd: add dax_operations support") Cc: stable@vger.kernel.org # 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);
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