mmc: sdhci: Fix potential ADMA descriptor table overflow

Change ADMA_TABLE_NO_ENTRIES to round the division up to fully
contain CONFIG_SYS_MMC_MAX_BLK_COUNT, fixing potential buffer overflow
of the ADMA descriptor table.

sdhci_prepare_adma_table() expecitily states it does _not_ check for
overflow as the descriptor table size is dependent on
CONFIG_SYS_MMC_MAX_BLK_COUNT. However, the ADMA_TABLE_NO_ENTRIES
calculation does not round up the divison, so with the current u-boot
 defaults:
max_mmc_transfer = (CONFIG_SYS_MMC_MAX_BLK_COUNT * MMC_MAX_BLOCK_LEN) =
65535 * 512 = 33553920 bytes.
ADMA_TABLE_NO_ENTRIES = max_mmc_transfer / ADMA_MAX_LEN =
33553920 / 65532, which does not divide cleanly.
actual_max_transfer = ADMA_TABLE_NO_ENTRIES * ADMA_MAX_LEN = 512 *
65532 = 33552384, which is smaller than max_mmc_transfer.
This can cause sdhci_prepare_adma_table() to write one extra
descriptor, overflowing the table when a transaction larger than
actual_max_transfer is issued.

Co-developed-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com>
Signed-off-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com>
Signed-off-by: Greg Malysa <greg.malysa@timesys.com>
Signed-off-by: Ian Roberts <ian.roberts@timesys.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>

diff --git a/include/sdhci.h b/include/sdhci.h
index d73a725609be359cd4bce1077f1e165011dd3070..2dd13b4c714a5c1d85c89aa0351a1303db0efcbb 100644 (file)
--- a/include/sdhci.h
+++ b/include/sdhci.h
@@ -11,6 +11,7 @@
 
 #include <linux/bitops.h>
 #include <linux/types.h>
+#include <linux/kernel.h>
 #include <asm/io.h>
 #include <mmc.h>
 #include <asm/gpio.h>
@@ -304,8 +305,8 @@ struct sdhci_ops {
 #else
 #define ADMA_DESC_LEN  8
 #endif
-#define ADMA_TABLE_NO_ENTRIES (CONFIG_SYS_MMC_MAX_BLK_COUNT * \
-                              MMC_MAX_BLOCK_LEN) / ADMA_MAX_LEN
+#define ADMA_TABLE_NO_ENTRIES DIV_ROUND_UP(CONFIG_SYS_MMC_MAX_BLK_COUNT * \
+                             MMC_MAX_BLOCK_LEN, ADMA_MAX_LEN)
 
 #define ADMA_TABLE_SZ (ADMA_TABLE_NO_ENTRIES * ADMA_DESC_LEN)