From: Jeremy Erazo Date: Tue, 12 May 2026 16:05:30 +0000 (+0000) Subject: usb: gadget: composite: fix integer underflow in WebUSB GET_URL handling X-Git-Tag: v7.1-rc6~9^2~39 X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=6c5dbc104dadd79fc2923497c20bae759a18758c;p=thirdparty%2Fkernel%2Flinux.git usb: gadget: composite: fix integer underflow in WebUSB GET_URL handling The WebUSB GET_URL handler in composite_setup() narrows landing_page_length to fit the host-supplied wLength using landing_page_length = w_length - WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_offset; If wLength is smaller than WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH the unsigned subtraction wraps, and the subsequent memcpy(url_descriptor->URL, cdev->landing_page + landing_page_offset, landing_page_length - landing_page_offset); ends up copying close to UINT_MAX bytes from cdev->landing_page into cdev->req->buf. KASAN reports a slab-out-of-bounds in composite_setup on the kmalloc-2k gadget_info allocation, and FORTIFY_SOURCE traps the memcpy as a 4294967293-byte field-spanning write into url_descriptor->URL (size 252). A USB host can reach this from a single SETUP packet against any gadget that has webusb/use=1 and a landingPage configured. Handle the small-wLength case before the math: when the host requested fewer bytes than the URL descriptor header, only the header is meaningful and no URL bytes need to be copied. Setting landing_page_length to landing_page_offset makes the existing memcpy a no-op and leaves the descriptor returned to the host unchanged for all larger wLength values. Fixes: 93c473948c58 ("usb: gadget: add WebUSB landing page support") Cc: stable Signed-off-by: Jeremy Erazo Link: https://patch.msgid.link/20260512160530.352318-1-mendozayt13@gmail.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c index a902184bdf82..dc3664374596 100644 --- a/drivers/usb/gadget/composite.c +++ b/drivers/usb/gadget/composite.c @@ -2172,7 +2172,10 @@ unknown: sizeof(url_descriptor->URL) - WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_offset); - if (w_length < WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_length) + if (w_length < WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH) + landing_page_length = landing_page_offset; + else if (w_length < + WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_length) landing_page_length = w_length - WEBUSB_URL_DESCRIPTOR_HEADER_LENGTH + landing_page_offset;