linux-kernel - [PATCH] mmc: dw_mmc: remove UBSAN warning in dw_mci_setup

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Date:	Wed, 08 Jun 2016 13:07:20 +0900
From:	Seung-Woo Kim <sw0312.kim@...sung.com>
To:	jh80.chung@...sung.com, ulf.hansson@...aro.org,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	sw0312.kim@...sung.com
Subject: [PATCH] mmc: dw_mmc: remove UBSAN warning in dw_mci_setup_bus()

This patch removes following UBSAN warnings in dw_mci_setup_bus().
The warnings are caused because of shift with more than 31 on 32
bit variable, so this patch fixes to shift only for less than 32.

  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
  [<ffffff9008d89ed4>] dw_mci_set_ios+0x184/0x798
  [<ffffff9008d550ac>] mmc_power_up+0x11c/0x260
  [<ffffff9008d56b78>] mmc_start_host+0x88/0x100
  [<ffffff9008d583f4>] mmc_add_host+0x6c/0x128
  [<ffffff9008d88f90>] dw_mci_probe+0x1088/0x1750
  [<ffffff9008d8caa8>] dw_mci_pltfm_register+0x108/0x178
  [<ffffff9008d8dae4>] dw_mci_exynos_probe+0x4c/0x88
  [<ffffff9008a03838>] platform_drv_probe+0x78/0x180
  [<ffffff90089fe9fc>] driver_probe_device+0x144/0x460
  [<ffffff90089fee0c>] __driver_attach+0xf4/0x140
  [<ffffff90089fad98>] bus_for_each_dev+0xf0/0x160
  [<ffffff90089fdc9c>] driver_attach+0x34/0x58
  [<ffffff90089fd3e0>] bus_add_driver+0x2c0/0x398
  [<ffffff9008a00924>] driver_register+0xbc/0x1e0
  [<ffffff9008a02a94>] __platform_driver_register+0x84/0xa8
  [<ffffff9009dd5730>] dw_mci_exynos_pltfm_driver_init+0x18/0x20
  [<ffffff9008082df8>] do_one_initcall+0xa0/0x2c8
  [<ffffff9009d81780>] kernel_init_freeable+0x52c/0x5dc
  [<ffffff9009519844>] kernel_init+0x1c/0xf8
  [<ffffff9008086e10>] ret_from_fork+0x10/0x40

Signed-off-by: Seung-Woo Kim <sw0312.kim@...sung.com>
---
 drivers/mmc/host/dw_mmc.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 2cc6123..dff045e 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 (((div < 32) ? (clock << div) : 0) != slot->__clk_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,
@@ -1129,7 +1130,7 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
 		mci_send_cmd(slot, sdmmc_cmd_bits, 0);
 
 		/* keep the clock with reflecting clock dividor */
-		slot->__clk_old = clock << div;
+		slot->__clk_old = (div < 32) ? (clock << div) : 0;
 	}
 
 	host->current_speed = clock;
-- 
1.7.4.1