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[83.31.79.248]) by smtp.gmail.com with ESMTPSA id c64sm710697lfg.70.2019.03.26.12.53.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Mar 2019 12:53:22 -0700 (PDT) Subject: Re: [PATCH v2 1/6] leds: netdev trigger: use memcpy in device_name_store To: Rasmus Villemoes , Pavel Machek , =?UTF-8?Q?Uwe_Kleine-K=c3=b6nig?= Cc: LKML , linux-leds@vger.kernel.org References: <20190313202615.22883-1-linux@rasmusvillemoes.dk> <20190314140619.3309-1-linux@rasmusvillemoes.dk> <20190314140619.3309-2-linux@rasmusvillemoes.dk> From: Jacek Anaszewski Message-ID: <987c3e60-edb3-44f0-be28-434c70bb8659@gmail.com> Date: Tue, 26 Mar 2019 20:53:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190314140619.3309-2-linux@rasmusvillemoes.dk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Rasmus, Thank you for the patch. On 3/14/19 3:06 PM, Rasmus Villemoes wrote: > If userspace doesn't end the input with a newline (which can easily > happen if the write happens from a C program that does write(fd, > iface, strlen(iface))), we may end up including garbage from a > previous, longer value in the device_name. For example > > # cat device_name > > # printf 'eth12' > device_name > # cat device_name > eth12 > # printf 'eth3' > device_name > # cat device_name > eth32 > > I highly doubt anybody is relying on this behaviour, so switch to > simply copying the bytes (we've already checked that size is < > IFNAMSIZ) and unconditionally zero-terminate it; of course, we also > still have to strip a trailing newline. > > This is also preparation for future patches. > > Signed-off-by: Rasmus Villemoes > --- > drivers/leds/trigger/ledtrig-netdev.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c > index 3dd3ed46d473..8d476b92f58c 100644 > --- a/drivers/leds/trigger/ledtrig-netdev.c > +++ b/drivers/leds/trigger/ledtrig-netdev.c > @@ -122,7 +122,8 @@ static ssize_t device_name_store(struct device *dev, > trigger_data->net_dev = NULL; > } > > - strncpy(trigger_data->device_name, buf, size); > + memcpy(trigger_data->device_name, buf, size); > + trigger_data->device_name[size] = 0; > if (size > 0 && trigger_data->device_name[size - 1] == '\n') > trigger_data->device_name[size - 1] = 0; > > Added tag: Fixes: 06f502f57d0d ("leds: trigger: Introduce a NETDEV trigger") and applied to the fixes-for-5.1-rc3 branch. -- Best regards, Jacek Anaszewski