CVE-2026-80827USB: serial: option: fix slab OOB read in interrupt URB callback

Official description

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 packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/fbe60fd2abc8a5561f39719a41ad9a01b5d8e567
• https://git.kernel.org/stable/c/94e5525697b9e91ddc4071129874120a50a4f342
• https://git.kernel.org/stable/c/6b8cf5422c7e96ed5b22a8368eff663f3f98b8ec
• https://git.kernel.org/stable/c/030e3a73d3c3aa67c44454649e984d6383cdb7d3
• https://git.kernel.org/stable/c/060db7d48af1e650643c8b8319111a9ea2ce4486
• https://git.kernel.org/stable/c/2ef5560387f2c0713cee975be2b24b281bd90f3e
• https://git.kernel.org/stable/c/a72a13c83a652516a0e469d275b81d29a7429049
• https://git.kernel.org/stable/c/d762aef4eba354066be21a5d88eb2066e282f4c9
• https://git.kernel.org/stable/c/885d802f544ca7bfa8f3984d94233cce715bb6b3