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

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.

Cc: <stable@kernel.org>
Reported-by: Robert Morris <rtm@mit.edu>
Closes: https://lore.kernel.org/linux-wireless/28782.1747258414@localhost/
Fixes: 7cb770729ba8 ("p54: move eeprom code into common library")
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Link: https://patch.msgid.link/20250516184107.47794-1-chunkeey@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>