linux-kernel - [PATCH 3.16 11/19] mmc: sunxi: avoid invalid pointer calculation

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Message-ID: <lsq.1491052670.67109106@decadent.org.uk>
Date:   Sat, 01 Apr 2017 14:17:50 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Arnd Bergmann" <arnd@...db.de>,
        "Ulf Hansson" <ulf.hansson@...aro.org>,
        "David Lanzendörfer" <david.lanzendoerfer@....ch>
Subject: [PATCH 3.16 11/19] mmc: sunxi: avoid invalid pointer calculation

3.16.43-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Arnd Bergmann <arnd@...db.de>

commit d34712d2e3db9b241d0484a6e3839c6b7ef9df78 upstream.

The sunxi mmc driver tries to calculate a dma address by using pointer
arithmetic, which causes a warning when dma_addr_t is wider than a pointer:

drivers/mmc/host/sunxi-mmc.c: In function 'sunxi_mmc_init_idma_des':
drivers/mmc/host/sunxi-mmc.c:296:35: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  struct sunxi_idma_des *pdes_pa = (struct sunxi_idma_des *)host->sg_dma;
                                   ^

To avoid this warning and to simplify the logic, this changes
the code to avoid the cast and calculate the correct address
manually. The behavior should be unchanged.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Acked-by: David Lanzendörfer <david.lanzendoerfer@....ch>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/mmc/host/sunxi-mmc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/mmc/host/sunxi-mmc.c
+++ b/drivers/mmc/host/sunxi-mmc.c
@@ -294,7 +294,7 @@ static void sunxi_mmc_init_idma_des(stru
 				    struct mmc_data *data)
 {
 	struct sunxi_idma_des *pdes = (struct sunxi_idma_des *)host->sg_cpu;
-	struct sunxi_idma_des *pdes_pa = (struct sunxi_idma_des *)host->sg_dma;
+	dma_addr_t next_desc = host->sg_dma;
 	int i, max_len = (1 << host->idma_des_size_bits);
 
 	for (i = 0; i < data->sg_len; i++) {
@@ -306,8 +306,9 @@ static void sunxi_mmc_init_idma_des(stru
 		else
 			pdes[i].buf_size = data->sg[i].length;
 
+		next_desc += sizeof(struct sunxi_idma_des);
 		pdes[i].buf_addr_ptr1 = sg_dma_address(&data->sg[i]);
-		pdes[i].buf_addr_ptr2 = (u32)&pdes_pa[i + 1];
+		pdes[i].buf_addr_ptr2 = (u32)next_desc;
 	}
 
 	pdes[0].config |= SDXC_IDMAC_DES0_FD;