wifi: p54: prevent buffer-overflow in p54_rx_eeprom_readback()

Summary

In the Linux kernel, the following vulnerability has been resolved: wifi: p54: prevent buffer-overflow in p54_rx_eeprom_readback() Robert Morris reported: |If a malicious USB device pretends to be an Intersil p54 wifi |interface and generates an eeprom_readback message with a large |eeprom->v1.len, p54_rx_eeprom_readback() will copy data from the |message beyond the end of priv->eeprom. | |static void p54_rx_eeprom_readback(struct p54_common *priv, | struct sk_buff *skb) |{ | struct p54_hdr *hdr = (struct p54_hdr *) skb->data; | struct p54_eeprom_lm86 *eeprom = (struct p54_eeprom_lm86 *) hdr->data; | | if (priv->fw_var >= 0x509) { | memcpy(priv->eeprom, eeprom->v2.data, | le16_to_cpu(eeprom->v2.len)); | } else { | memcpy(priv->eeprom, eeprom->v1.data, | le16_to_cpu(eeprom->v1.len)); | } | [...] The eeprom->v{1,2}.len is set by the driver in p54_download_eeprom(). The device is supposed to provide the same length back to the driver. But yes, it's possible (like shown in the report) to alter the value to something that causes a crash/panic due to overrun. This patch addresses the issue by adding the size to the common device context, so p54_rx_eeprom_readback no longer relies on possibly tampered values... That said, it also checks if the "firmware" altered the value and no longer copies them. The one, small saving grace is: Before the driver tries to read the eeprom, it needs to upload >a< firmware. the vendor firmware has a proprietary license and as a reason, it is not present on most distributions by default.