[PATCH 6.1 181/185] cxl/region:Fix overflow issue in alloc_hpa()

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6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Quanquan Cao <caoqq@xxxxxxxxxxx>

commit d76779dd3681c01a4c6c3cae4d0627c9083e0ee6 upstream.

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: Quanquan Cao <caoqq@xxxxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Fixes: 23a22cd1c98b ("cxl/region: Allocate HPA capacity to regions")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/cxl/core/region.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -450,7 +450,7 @@ static int alloc_hpa(struct cxl_region *
 	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);
 
@@ -470,7 +470,7 @@ static int alloc_hpa(struct cxl_region *
 	    (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;
 






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