wifi: p54: validate RX frame length in p54_rx_eeprom_readback()

In the Linux kernel, the following vulnerability has been resolved: wifi: p54: validate RX frame length in p54_rx_eeprom_readback() p54_rx_eeprom_readback() copies the requested EEPROM slice out of a device-supplied readback frame without checking that the skb actually holds that many bytes. Commit da1b9a55ff11 ("wifi: p54: prevent buffer-overflow in p54_rx_eeprom_readback()") closed the destination overflow by copying a fixed priv->eeprom_slice_size (and rejecting a mismatched advertised len), but the source side is still unbounded: nothing verifies the frame is long enough to supply that many bytes. A malicious USB device can send a short frame whose advertised len matches priv->eeprom_slice_size while the payload is truncated. The equality check passes and memcpy() reads past the end of the skb, leaking adjacent heap: BUG: KASAN: slab-out-of-bounds in p54_rx (drivers/net/wireless/intersil/p54/txrx.c:507) Read of size 1016 at addr ffff88800f077114 by task swapper/0/0 Call Trace: <IRQ> ... __asan_memcpy (mm/kasan/shadow.c:105) p54_rx (drivers/net/wireless/intersil/p54/txrx.c:507) p54u_rx_cb (drivers/net/wireless/intersil/p54/p54usb.c:163) __usb_hcd_giveback_urb (drivers/usb/core/hcd.c:1657) dummy_timer (drivers/usb/gadget/udc/dummy_hcd.c:2005) ... </IRQ> The buggy address belongs to the object at ffff88800f0770c0 which belongs to the cache skbuff_small_head of size 704 The buggy address is located 84 bytes inside of allocated 704-byte region [ffff88800f0770c0, ffff88800f077380) Check that the slice fits in the skb before copying.