spi: Fix erroneous sgs value with min_t()

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@linux-foundation.org>
Suggested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20220316175317.465-1-biju.das.jz@bp.renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 6937cf2..c4dd120 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1000,10 +1000,10 @@ 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;