USB: serial: option: fix slab OOB read in interrupt URB callback

Overview

In the Linux kernel, the following vulnerability has been resolved:

USB: serial: option: fix slab OOB read in interrupt URB callback

The interrupt URB buffer is allocated in setup_port_interrupt_in() based on the endpoint's wMaxPacketSize:

buffer_size = usb_endpoint_maxp(epd);
port->interrupt_in_buffer = kmalloc(buffer_size, GFP_KERNEL);

When a USB device declares wMaxPacketSize = 8 on its interrupt IN endpoint, the buffer is allocated from kmalloc-8 cache (exactly 8 bytes).

If the device sends a short packet (actual_length < wMaxPacketSize), the URB completes with status == 0 and the callback proceeds to read:

data[sizeof(struct usb_ctrlrequest)]

which evaluates to data[8], accessing 1 byte beyond the allocated 8-byte buffer. This results in a slab out-of-bounds read.

Fix this by adding the missing bounds check: first verify that the actual length is large enough to contain the struct usb_ctrlrequest header before accessing req_pkt->bRequestType and req_pkt->bRequest, and then verify that there is an additional byte for the modem signal state before reading data[sizeof(struct usb_ctrlrequest)] inside the conditional. Use sizeof(*req_pkt) instead of sizeof(struct usb_ctrlrequest) for consistency.

[ johan: use dev_err(); split signals declaration and initialisation ]

Affected

• Linux >= 58cfe9113e485f7e04bd0eac4fc4251b330af501 < fbe60fd2abc8a5561f39719a41ad9a01b5d8e567
• Linux >= 58cfe9113e485f7e04bd0eac4fc4251b330af501 < 94e5525697b9e91ddc4071129874120a50a4f342
• Linux >= 58cfe9113e485f7e04bd0eac4fc4251b330af501 < 6b8cf5422c7e96ed5b22a8368eff663f3f98b8ec
• Linux >= 58cfe9113e485f7e04bd0eac4fc4251b330af501 < 030e3a73d3c3aa67c44454649e984d6383cdb7d3
• Linux >= 58cfe9113e485f7e04bd0eac4fc4251b330af501 < 060db7d48af1e650643c8b8319111a9ea2ce4486
• Linux >= 58cfe9113e485f7e04bd0eac4fc4251b330af501 < 2ef5560387f2c0713cee975be2b24b281bd90f3e
• Linux >= 58cfe9113e485f7e04bd0eac4fc4251b330af501 < a72a13c83a652516a0e469d275b81d29a7429049
• Linux >= 58cfe9113e485f7e04bd0eac4fc4251b330af501 < d762aef4eba354066be21a5d88eb2066e282f4c9
• Linux >= 58cfe9113e485f7e04bd0eac4fc4251b330af501 < 885d802f544ca7bfa8f3984d94233cce715bb6b3
• Linux 2.6.12

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.