Commit 02a48436 authored Sep 13, 2017 by Mikulas Patocka Committed by Jens Axboe Sep 25, 2017

brd: fix overflow in __brd_direct_access



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.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 1647b9b9 ("brd: add dax_operations support")
Cc: stable@vger.kernel.org	# 4.12+
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 820bf5c4

drivers/block/brd.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -342,7 +342,7 @@ static long __brd_direct_access(struct brd_device *brd, pgoff_t pgoff,

		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);