Commit d76779dd authored by Quanquan Cao's avatar Quanquan Cao Committed by Dan Williams
Browse files

cxl/region：Fix overflow issue in alloc_hpa() 



Creating a region with 16 memory devices caused a problem. The div_u64_rem
function, used for dividing an unsigned 64-bit number by a 32-bit one,
faced an issue when SZ_256M * p->interleave_ways. The result surpassed
the maximum limit of the 32-bit divisor (4G), leading to an overflow
and a remainder of 0.
note: At this point, p->interleave_ways is 16, meaning 16 * 256M = 4G

To fix this issue, I replaced the div_u64_rem function with div64_u64_rem
and adjusted the type of the remainder.

Signed-off-by: default avatarQuanquan Cao <caoqq@fujitsu.com>
Reviewed-by: default avatarDave Jiang <dave.jiang@intel.com>
Fixes: 23a22cd1 ("cxl/region: Allocate HPA capacity to regions")
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent d72a4caf

drivers/cxl/core/region.c

+2 −2
Original line number Diff line number Diff line
@@ -525,7 +525,7 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size) 
	struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(cxlr->dev.parent);

	struct cxl_region_params *p = &cxlr->params;

	struct resource *res;

	u32 remainder = 0;

	u64 remainder = 0;



	lockdep_assert_held_write(&cxl_region_rwsem);
@@ -545,7 +545,7 @@ static int alloc_hpa(struct cxl_region *cxlr, resource_size_t size) 
	    (cxlr->mode == CXL_DECODER_PMEM && uuid_is_null(&p->uuid)))

		return -ENXIO;



	div_u64_rem(size, SZ_256M * p->interleave_ways, &remainder);

	div64_u64_rem(size, (u64)SZ_256M * p->interleave_ways, &remainder);

	if (remainder)

		return -EINVAL;