CVE-2026-31616usb: gadget: f_phonet: fix skb frags[] overflow in pn_rx_complete()

Official description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_phonet: fix skb frags[] overflow in pn_rx_complete() A broken/bored/mean USB host can overflow the skb_shared_info->frags[] array on a Linux gadget exposing a Phonet function by sending an unbounded sequence of full-page OUT transfers. pn_rx_complete() finalizes the skb only when req->actual < req->length, where req->length is set to PAGE_SIZE by the gadget. If the host always sends exactly PAGE_SIZE bytes per transfer, fp->rx.skb will never be reset and each completion will add another fragment via skb_add_rx_frag(). Once nr_frags exceeds MAX_SKB_FRAGS (default 17), subsequent frag stores overwrite memory adjacent to the shinfo on the heap. Drop the skb and account a length error when the frag limit is reached, matching the fix applied in t7xx by commit f0813bcd2d9d ("net: wwan: t7xx: fix potential skb->frags overflow in RX path").

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/3d7f7e0c842242878c24b2facff8d6eda23ee1e9
• https://git.kernel.org/stable/c/b5ec49fa198bd08967a3102bd41f53ccadce72c9
• https://git.kernel.org/stable/c/7424f0287da73d3d8c5fa5e9d25d26fce762708e
• https://git.kernel.org/stable/c/9ceff1251904901b0b4e5fe6350fcaffa368ce83
• https://git.kernel.org/stable/c/c9315ce9da3632c591666a29de82d3e92d46bec1
• https://git.kernel.org/stable/c/4e476c25bfcab0535ba7c76a903ae77ca8747711
• https://git.kernel.org/stable/c/bd44ce09b9b569f49ed13e2d87d23d853fc7d6a7
• https://git.kernel.org/stable/c/66f7471c4042e4eb300e30b5b9d87d1406862673
• https://git.kernel.org/stable/c/c088d5dd2fffb4de1fb8e7f57751c8b82942180a