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[109.49.32.45]) by smtp.gmail.com with ESMTPSA id p18-20020adf9d92000000b0033e18f5714esm5454212wre.59.2024.03.02.07.18.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 02 Mar 2024 07:18:14 -0800 (PST) From: Rui Miguel Silva To: Mikhail Lobanov Cc: Mikhail Lobanov , Greg Kroah-Hartman , greybus-dev@lists.linaro.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] greybus: Fix deref of NULL in __gb_lights_flash_brightness_set In-Reply-To: <20240301190425.120605-1-m.lobanov@rosalinux.ru> References: <20240301190425.120605-1-m.lobanov@rosalinux.ru> Date: Sat, 02 Mar 2024 15:18:13 +0000 Message-ID: Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Hi Mikhail, Thanks for your patch. Mikhail Lobanov writes: > Dereference of null pointer in the __gb_lights_flash_brightness_set function. > Assigning the channel the result of executing the get_channel_from_mode function > without checking for NULL may result in an error. > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > Fixes: 2870b52bae4c ("greybus: lights: add lights implementation") > Signed-off-by: Mikhail Lobanov Yeah, at the time when this was implemented I recall that we could only set the brightness of the torch mode in a flash led, not in the flash only mode. So, if we were getting here was that for sure we had a torch channel and get_channel_from_mode will always find a channel, so never returning null here. but yeah, this is safer. but maybe just do something like the bellow would be simpler: modified drivers/staging/greybus/light.c @@ -147,6 +147,9 @@ static int __gb_lights_flash_brightness_set(struct gb_channel *channel) channel = get_channel_from_mode(channel->light, GB_CHANNEL_MODE_TORCH); + if (!channel) + return -EINVAL; + /* For not flash we need to convert brightness to intensity */ intensity = channel->intensity_uA.min + (channel->intensity_uA.step * channel->led->brightness); what do you think? Cheers, Rui > --- > drivers/staging/greybus/light.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/staging/greybus/light.c b/drivers/staging/greybus/light.c > index 87d36948c610..929514350947 100644 > --- a/drivers/staging/greybus/light.c > +++ b/drivers/staging/greybus/light.c > @@ -148,10 +148,15 @@ static int __gb_lights_flash_brightness_set(struct gb_channel *channel) > GB_CHANNEL_MODE_TORCH); > > /* For not flash we need to convert brightness to intensity */ > - intensity = channel->intensity_uA.min + > + > + if (channel) { > + intensity = channel->intensity_uA.min + > (channel->intensity_uA.step * channel->led->brightness); > > - return __gb_lights_flash_intensity_set(channel, intensity); > + return __gb_lights_flash_intensity_set(channel, intensity); > + } > + > + return 0; > } > #else > static struct gb_channel *get_channel_from_cdev(struct led_classdev *cdev) > -- > 2.43.0