[PATCH v2] mmc: dw_mmc: remove UBSAN warning in dw_mci_setup_bus()

Seung-Woo Kim
2016-06-17T05:16:49Z

This patch removes following UBSAN warnings in dw_mci_setup_bus().

UBSAN: Undefined behaviour in drivers/mmc/host/dw_mmc.c:1102:14
shift exponent 250 is too large for 32-bit type 'unsigned int'
Call trace:
[<ffffff90080908a8>] dump_backtrace+0x0/0x380
[<ffffff9008090c3c>] show_stack+0x14/0x20
[<ffffff90087457b8>] dump_stack+0xe0/0x120
[<ffffff90087b1360>] ubsan_epilogue+0x18/0x68
[<ffffff90087b1a94>] __ubsan_handle_shift_out_of_bounds+0x18c/0x1bc
[<ffffff9008d89cb8>] dw_mci_setup_bus+0x3a0/0x438
[...]

UBSAN: Undefined behaviour in drivers/mmc/host/dw_mmc.c:1132:27
shift exponent 250 is too large for 32-bit type 'unsigned int'
Call trace:
[<ffffff90080908a8>] dump_backtrace+0x0/0x380
[<ffffff9008090c3c>] show_stack+0x14/0x20
[<ffffff90087457b8>] dump_stack+0xe0/0x120
[<ffffff90087b1360>] ubsan_epilogue+0x18/0x68
[<ffffff90087b1a94>] __ubsan_handle_shift_out_of_bounds+0x18c/0x1bc
[<ffffff9008d89c9c>] dw_mci_setup_bus+0x384/0x438
[...]

The warnings are caused because of shift with more than 31 on 32
bit variable, so this patch fixes to keep both clock and divider
instead of shift.

Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
---
drivers/mmc/host/dw_mmc.c | 8 +++++---
drivers/mmc/host/dw_mmc.h | 8 +++++---
2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 2cc6123..d05c8cc 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -1099,7 +1099,8 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)

div = (host->bus_hz != clock) ? DIV_ROUND_UP(div, 2) : 0;

- if ((clock << div) != slot->__clk_old || force_clkinit)
+ if (clock != slot->__clk_old || div != slot->__div_old ||
+ force_clkinit)
dev_info(&slot->mmc->class_dev,
"Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ div = %d)\n",
slot->id, host->bus_hz, clock,
@@ -1128,8 +1129,9 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
/* inform CIU */
mci_send_cmd(slot, sdmmc_cmd_bits, 0);

- /* keep the clock with reflecting clock dividor */
- slot->__clk_old = clock << div;
+ /* keep the clock and clock divider */
+ slot->__clk_old = clock;
+ slot->__div_old = div;
}

host->current_speed = clock;
diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
index 1e8d838..fdfc3f5 100644
--- a/drivers/mmc/host/dw_mmc.h
+++ b/drivers/mmc/host/dw_mmc.h
@@ -245,9 +245,10 @@ extern int dw_mci_resume(struct dw_mci *host);
* @queue_node: List node for placing this node in the @queue list of
* &struct dw_mci.
* @clock: Clock rate configured by set_ios(). Protected by host->lock.
- * @__clk_old: The last updated clock with reflecting clock divider.
- * Keeping track of this helps us to avoid spamming the console
- * with CONFIG_MMC_CLKGATE.
+ * @__clk_old: The last updated clock.
+ * @__div_old: The last updated clock divider.
+ * Keeping track of clock and clock divider helps us to avoid spamming
+ * the console with CONFIG_MMC_CLKGATE.
* @flags: Random state bits associated with the slot.
* @id: Number of this slot.
* @sdio_id: Number of this slot in the SDIO interrupt registers.
@@ -263,6 +264,7 @@ struct dw_mci_slot {

unsigned int clock;
unsigned int __clk_old;
+ unsigned int __div_old;

unsigned long flags;
#define DW_MMC_CARD_PRESENT 0
--
1.7.4.1