From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jaehoon Chung Subject: Re: [PATCH] mmc: dw_mmc: remove UBSAN warning in dw_mci_setup_bus() Date: Thu, 09 Jun 2016 21:38:22 +0900 Message-ID: <5759633E.7090706@samsung.com> References: <1465358840-22826-1-git-send-email-sw0312.kim@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from mailout2.samsung.com ([203.254.224.25]:47546 "EHLO mailout2.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751199AbcFIMia (ORCPT ); Thu, 9 Jun 2016 08:38:30 -0400 In-reply-to: <1465358840-22826-1-git-send-email-sw0312.kim@samsung.com> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Seung-Woo Kim , ulf.hansson@linaro.org, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org Hi Seung-Woo, On 06/08/2016 01:07 PM, Seung-Woo Kim wrote: > 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: > [] dump_backtrace+0x0/0x380 > [] show_stack+0x14/0x20 > [] dump_stack+0xe0/0x120 > [] ubsan_epilogue+0x18/0x68 > [] __ubsan_handle_shift_out_of_bounds+0x18c/0x1bc > [] 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: > [] dump_backtrace+0x0/0x380 > [] show_stack+0x14/0x20 > [] dump_stack+0xe0/0x120 > [] ubsan_epilogue+0x18/0x68 > [] __ubsan_handle_shift_out_of_bounds+0x18c/0x1bc > [] dw_mci_setup_bus+0x384/0x438 The below message can be discarded. > [] dw_mci_set_ios+0x184/0x798 > [] mmc_power_up+0x11c/0x260 > [] mmc_start_host+0x88/0x100 > [] mmc_add_host+0x6c/0x128 > [] dw_mci_probe+0x1088/0x1750 > [] dw_mci_pltfm_register+0x108/0x178 > [] dw_mci_exynos_probe+0x4c/0x88 > [] platform_drv_probe+0x78/0x180 > [] driver_probe_device+0x144/0x460 > [] __driver_attach+0xf4/0x140 > [] bus_for_each_dev+0xf0/0x160 > [] driver_attach+0x34/0x58 > [] bus_add_driver+0x2c0/0x398 > [] driver_register+0xbc/0x1e0 > [] __platform_driver_register+0x84/0xa8 > [] dw_mci_exynos_pltfm_driver_init+0x18/0x20 > [] do_one_initcall+0xa0/0x2c8 > [] kernel_init_freeable+0x52c/0x5dc > [] kernel_init+0x1c/0xf8 > [] ret_from_fork+0x10/0x40 > > Signed-off-by: Seung-Woo Kim > --- > 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 || Well, we don't expect that clock is 0. if clock is 0, it should be passed to " if (!clock)".. During initializing card, clock is 400KHz or less..I understood what you want to fix. But I taught this is not correct. > + 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; Also, clock is not 0.. Best Regards, Jaehoon Chung > } > > host->current_speed = clock; >