Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965104AbeAJJJS (ORCPT + 1 other); Wed, 10 Jan 2018 04:09:18 -0500 Received: from mail1.windriver.com ([147.11.146.13]:51657 "EHLO mail1.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755064AbeAJJIj (ORCPT ); Wed, 10 Jan 2018 04:08:39 -0500 Subject: Re: [PATCH, v2] arm: omap2: timer: fix a kmemleak caused in omap_get_timer_dt To: Ladislav Michl CC: , , , , References: <1515489861-1474-1-git-send-email-qi.hou@windriver.com> <20180109115222.GA28346@lenoch> From: qhou Message-ID: <1458dc6c-bc5f-2a78-2e42-aacfe4328460@windriver.com> Date: Wed, 10 Jan 2018 17:08:12 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20180109115222.GA28346@lenoch> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [128.224.162.179] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On 2018年01月09日 19:52, Ladislav Michl wrote: > On Tue, Jan 09, 2018 at 05:24:21PM +0800, Qi Hou wrote: > > When more than one GP timers are used as kernel system timers and the > > corresponding nodes in device-tree are marked with the same "disabled" > > property, then the "attr" field of the property will be initialized > > more than once as the property being added to sys file system via > > __of_add_property_sysfs(). > > > > In __of_add_property_sysfs(), the "name" field of pp->attr.attr is set > > directly to the return value of safe_name(), without taking care of > > whether it's already a valid pointer to a memory block. If it is, its > > old value will always be overwritten by the new one and the memory block > > allocated before will a "ghost", then a kmemleak happened. > > As timers does not seem to be deallocated, this does not matter in practice. > Fix eats a bit more from heap. Yes, there is no timers being deallocated, as I see. But it is not eligible that sharing the same property among different device nodes. And itexposes kernel info to users. That is not safe. The fix causes a tiny consumption of heap, maybe it's worth. -- best regards, Qi Hou > > > That the same "disabled" property being added to different nodes of device > > tree would cause that kind of kmemleak overhead, at leat once. > > > > To fix it, allocate the property dynamically, and delete static one. > > > > Signed-off-by: Qi Hou > > --- > > arch/arm/mach-omap2/timer.c | 19 +++++++++++-------- > > 1 file changed, 11 insertions(+), 8 deletions(-) > > > > diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c > > index ece09c9..206ae8d 100644 > > --- a/arch/arm/mach-omap2/timer.c > > +++ b/arch/arm/mach-omap2/timer.c > > @@ -156,12 +156,6 @@ static struct clock_event_device clockevent_gpt = { > > .tick_resume = omap2_gp_timer_shutdown, > > }; > > > > -static struct property device_disabled = { > > - .name = "status", > > - .length = sizeof("disabled"), > > - .value = "disabled", > > -}; > > - > > static const struct of_device_id omap_timer_match[] __initconst = { > > { .compatible = "ti,omap2420-timer", }, > > { .compatible = "ti,omap3430-timer", }, > > @@ -203,8 +197,17 @@ static struct device_node * __init omap_get_timer_dt(const struct of_device_id * > > of_get_property(np, "ti,timer-secure", NULL))) > > continue; > > > > - if (!of_device_is_compatible(np, "ti,omap-counter32k")) > > - of_add_property(np, &device_disabled); > > + if (!of_device_is_compatible(np, "ti,omap-counter32k")) { > > + struct property *prop; > > + > > + prop = kzalloc(sizeof(*prop), GFP_KERNEL); > > + if (!prop) > > + return NULL; > > + prop->name = "status"; > > + prop->length = sizeof("disabled"); > > + prop->value = "disabled"; > > How about (see drivers/of/unittest.c)? > prop->value = "disabled"; > prop->length = strlen(prop->value); It's better. I will do that. thanks, Qi Hou > > > + of_add_property(np, prop); > > + } > > return np; > > } > > > > -- > > 2.7.4 > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Best regards, Qi Hou Phone number: +86-10-8477-8608 Address: Floor 15, Building B, Wangjing Plaza, No.9 Zhong-Huan Nanlu, Chaoyang District