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([2a01:e34:ed2f:f020:6186:703a:2abc:2187]) by smtp.googlemail.com with ESMTPSA id p4sm2882929wmc.46.2020.11.17.00.57.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Nov 2020 00:57:30 -0800 (PST) Subject: Re: [PATCH] thermal: Fix NULL pointer dereference issue To: Zhang Rui , Mukesh Ojha , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: amitk@kernel.org References: <1605544181-5348-1-git-send-email-mojha@codeaurora.org> <4e28affd89ba8a852e0fb7ace076458b3d43839a.camel@intel.com> From: Daniel Lezcano Message-ID: Date: Tue, 17 Nov 2020 09:57:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <4e28affd89ba8a852e0fb7ace076458b3d43839a.camel@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/11/2020 08:18, Zhang Rui wrote: > On Mon, 2020-11-16 at 21:59 +0530, Mukesh Ojha wrote: >> Cooling stats variable inside thermal_cooling_device_stats_update() >> can get NULL. We should add a NULL check on stat inside for sanity. >> >> Signed-off-by: Mukesh Ojha >> --- >> drivers/thermal/thermal_sysfs.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/thermal/thermal_sysfs.c >> b/drivers/thermal/thermal_sysfs.c >> index a6f371f..f52708f 100644 >> --- a/drivers/thermal/thermal_sysfs.c >> +++ b/drivers/thermal/thermal_sysfs.c >> @@ -754,6 +754,9 @@ void thermal_cooling_device_stats_update(struct >> thermal_cooling_device *cdev, >> { >> struct cooling_dev_stats *stats = cdev->stats; >> >> + if (!stats) >> + return; >> + > May I know in which case stats can be NULL? > The only possibility I can see is that cdev->ops->get_max_state() fails > in cooling_device_stats_setup(), right? A few lines below, the allocation could fail. stats = kzalloc(var, GFP_KERNEL); if (!stats) return; Some drivers define themselves as a cooling device state to let the userspace to act on their power. The screen brightness is one example with a cdev with 1024 states, the resulting stats table to be allocated is very big and the kzalloc is prone to fail. > thanks, > rui > >> spin_lock(&stats->lock); >> >> if (stats->state == new_state) > -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog