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([2a00:1fa0:8bd:44ed:dbe:39ab:66f8:7790]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-556383d8dccsm1904273e87.66.2025.07.09.01.48.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Jul 2025 01:48:33 -0700 (PDT) Message-ID: Date: Wed, 9 Jul 2025 11:48:32 +0300 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] usb: gadget: configfs: Fix OOB read on empty string write To: Xinyu Liu <1171169449@qq.com>, gregkh@linuxfoundation.org Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, katieeliu@tencent.com, security@tencent.com References: Content-Language: en-US From: Sergey Shtylyov In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/9/25 6:55 AM, Xinyu Liu wrote: > When writing an empty string to either 'qw_sign' or 'landingPage' > sysfs attributes, the store functions attempt to access page[l - 1] > before validating that the length 'l' is greater than zero. > > This patch fixes the vulnerability by adding a check at the beginning > of os_desc_qw_sign_store() and webusb_landingPage_store() to handle > the zero-length input case gracefully by returning immediately. > > Signed-off-by: Xinyu Liu > --- > drivers/usb/gadget/configfs.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c > index fba2a56dae97..1bb32d6be9b3 100644 > --- a/drivers/usb/gadget/configfs.c > +++ b/drivers/usb/gadget/configfs.c > @@ -1064,7 +1064,8 @@ static ssize_t webusb_landingPage_store(struct config_item *item, const char *pa > struct gadget_info *gi = webusb_item_to_gadget_info(item); > unsigned int bytes_to_strip = 0; > int l = len; > - Why are you removing empty line here? > + if (!len) > + return len; > if (page[l - 1] == '\n') { > --l; > ++bytes_to_strip; > @@ -1187,7 +1188,8 @@ static ssize_t os_desc_qw_sign_store(struct config_item *item, const char *page, > { > struct gadget_info *gi = os_desc_item_to_gadget_info(item); > int res, l; > - And here? > + if (!len) > + return len; > l = min_t(int, len, OS_STRING_QW_SIGN_LEN >> 1); > if (page[l - 1] == '\n') > --l; MBR, Sergey