[PATCH 4.19 010/338] spi: Fix erroneous sgs value with min_t()

[Greg Kroah-Hartman]

From: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>

[ Upstream commit ebc4cb43ea5ada3db46c80156fca58a54b9bbca8 ]

While computing sgs in spi_map_buf(), the data type
used in min_t() for max_seg_size is 'unsigned int' where
as that of ctlr->max_dma_len is 'size_t'.

min_t(unsigned int,x,y) gives wrong results if one of x/y is
'size_t'

Consider the below examples on a 64-bit machine (ie size_t is
64-bits, and unsigned int is 32-bit).
    case 1) min_t(unsigned int, 5, 0x100000001);
    case 2) min_t(size_t, 5, 0x100000001);

Case 1 returns '1', where as case 2 returns '5'. As you can see
the result from case 1 is wrong.

This patch fixes the above issue by using the data type of the
parameters that are used in min_t with maximum data length.

Fixes: commit 1a4e53d2fc4f68aa ("spi: Fix invalid sgs value")
Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Suggested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220316175317.465-1-biju.das.jz@xxxxxxxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/spi/spi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 518c8e0eef7f..3bcd6f178f73 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -779,10 +779,10 @@ int spi_map_buf(struct spi_controller *ctlr, struct device *dev,
 	int i, ret;
 
 	if (vmalloced_buf || kmap_buf) {
-		desc_len = min_t(unsigned int, max_seg_size, PAGE_SIZE);
+		desc_len = min_t(unsigned long, max_seg_size, PAGE_SIZE);
 		sgs = DIV_ROUND_UP(len + offset_in_page(buf), desc_len);
 	} else if (virt_addr_valid(buf)) {
-		desc_len = min_t(unsigned int, max_seg_size, ctlr->max_dma_len);
+		desc_len = min_t(size_t, max_seg_size, ctlr->max_dma_len);
 		sgs = DIV_ROUND_UP(len, desc_len);
 	} else {
 		return -EINVAL;
-- 
2.34.1