usbnet: gl620a: fix out-of-bounds read in genelink_rx_fixup()

Overview

In the Linux kernel, the following vulnerability has been resolved:

usbnet: gl620a: fix out-of-bounds read in genelink_rx_fixup()

genelink_rx_fixup() splits an aggregated RX frame into its individual packets, using a per-packet length taken from device-supplied data. That length is only bounded by GL_MAX_PACKET_LEN (1514); it is never compared against how many bytes were actually received.

A malicious GeneLink (GL620A) device can therefore send a short URB whose header claims packet_count > 1 and a first packet of up to 1514 bytes.

skb_put_data(gl_skb, packet->packet_data, size);

then copies past the end of the receive buffer and hands the adjacent slab contents up the network stack, an out-of-bounds read that leaks kernel heap. No privilege is required: the path runs in the usbnet RX softirq as soon as the interface is up.

BUG: KASAN: slab-out-of-bounds in genelink_rx_fixup (drivers/net/usb/gl620a.c:112) Read of size 1514 at addr ffff888011309708 by task ksoftirqd/0/14 Call Trace: ... __asan_memcpy (mm/kasan/shadow.c:105) genelink_rx_fixup (include/linux/skbuff.h:2814 drivers/net/usb/gl620a.c:112) usbnet_bh (drivers/net/usb/usbnet.c:572 drivers/net/usb/usbnet.c:1589) process_one_work (kernel/workqueue.c:3322) bh_worker (kernel/workqueue.c:3405) tasklet_action (kernel/softirq.c:965) handle_softirqs (kernel/softirq.c:622) run_ksoftirqd (kernel/softirq.c:1076) ...

skb_pull() already verifies that the requested length fits the buffer and returns NULL otherwise. Move it ahead of the copy and check its result, so a packet that overruns the received data is rejected before it is read. Well-formed frames, whose packets are fully present, are unaffected.

Affected

• Linux >= 47ee3051c856cc2aa95d35d577a8cb37279d540f < 255d03551f94c7bdd86c7d9181a70b21917d829f
• Linux >= 47ee3051c856cc2aa95d35d577a8cb37279d540f < 4359376e6238d89977a35086e47ca3b07f43e850
• Linux >= 47ee3051c856cc2aa95d35d577a8cb37279d540f < 8624e179fa3ce23c2fbd1a198ce30764b73f054a
• Linux >= 47ee3051c856cc2aa95d35d577a8cb37279d540f < 573418f7ea8f859a841417eb4b915594094fd967
• Linux >= 47ee3051c856cc2aa95d35d577a8cb37279d540f < 0575599e451aff3c5329922562374a2cab25fc51
• Linux >= 47ee3051c856cc2aa95d35d577a8cb37279d540f < 0a7d9c7c5f1f208c523abbb4db6aea7bc1fad3db
• Linux >= 47ee3051c856cc2aa95d35d577a8cb37279d540f < 3ef79fa3860e644c8de7834fa7300e1c58f38862
• Linux >= 47ee3051c856cc2aa95d35d577a8cb37279d540f < 8ff7f2a6da4fccaa5cc9be7251a24e71e29fbd1a
• Linux 2.6.14

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.