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guard acm_open endpoint reads against short bLength descriptors

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Javid Khan
2026-07-03 22:53:06 +05:30
parent 8a2d00f330
commit 28daf9eb87
1 changed files with 7 additions and 4 deletions
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11
src/class/cdc/cdc_host.c
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@ -716,7 +716,9 @@ bool cdch_xfer_cb(uint8_t daddr, uint8_t ep_addr, xfer_result_t event, uint32_t
//--------------------------------------------------------------------+
static bool open_ep_stream_pair(cdch_interface_t *p_cdc, tusb_desc_endpoint_t const *desc_ep) {
for (size_t i = 0; i < 2; i++) {
TU_ASSERT(TUSB_DESC_ENDPOINT == desc_ep->bDescriptorType && TUSB_XFER_BULK == desc_ep->bmAttributes.xfer, 0);
// pin bLength so tu_desc_next() below cannot walk the second endpoint past a caller-checked bound
TU_ASSERT(sizeof(tusb_desc_endpoint_t) == desc_ep->bLength &&
TUSB_DESC_ENDPOINT == desc_ep->bDescriptorType && TUSB_XFER_BULK == desc_ep->bmAttributes.xfer, 0);
TU_ASSERT(tuh_edpt_open(p_cdc->daddr, desc_ep));
const uint8_t ep_dir = tu_edpt_dir(desc_ep->bEndpointAddress);
tu_edpt_stream_t *stream = (ep_dir == TUSB_DIR_IN) ? &p_cdc->stream.rx : &p_cdc->stream.tx;
@ -1031,7 +1033,8 @@ static uint16_t acm_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, u
// Open notification endpoint of control interface if any
if (itf_desc->bNumEndpoints == 1) {
TU_ASSERT(tu_desc_in_bounds(p_desc, desc_end), 0);
// whole endpoint descriptor must fit: tuh_edpt_open reads the full struct regardless of bLength
TU_ASSERT(p_desc + sizeof(tusb_desc_endpoint_t) <= desc_end, 0);
TU_ASSERT(TUSB_DESC_ENDPOINT == tu_desc_type(p_desc), 0);
const tusb_desc_endpoint_t *desc_ep = (const tusb_desc_endpoint_t *)p_desc;
TU_ASSERT(tuh_edpt_open(daddr, desc_ep), 0);
@ -1041,13 +1044,13 @@ static uint16_t acm_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, u
}
//------------- Data Interface (if any) -------------//
if (tu_desc_in_bounds(p_desc, desc_end) && TUSB_DESC_INTERFACE == tu_desc_type(p_desc)) {
if (p_desc + sizeof(tusb_desc_interface_t) <= desc_end && TUSB_DESC_INTERFACE == tu_desc_type(p_desc)) {
const tusb_desc_interface_t *data_itf = (const tusb_desc_interface_t *)p_desc;
if (data_itf->bInterfaceClass == TUSB_CLASS_CDC_DATA) {
p_desc = tu_desc_next(p_desc); // next to endpoint descriptor
// data endpoints expected to be in pairs, make sure both fit before reading them
TU_ASSERT((uint16_t)(desc_end - p_desc) >= 2 * sizeof(tusb_desc_endpoint_t), 0);
TU_ASSERT(p_desc + 2 * sizeof(tusb_desc_endpoint_t) <= desc_end, 0);
TU_ASSERT(open_ep_stream_pair(p_cdc, (const tusb_desc_endpoint_t *)p_desc), 0);
p_desc += data_itf->bNumEndpoints * sizeof(tusb_desc_endpoint_t);
}