TLDRVuln - Cybersecurity Vulnerabilities Made Simple

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

ixgbe: Fix NULL pointer dereference in ixgbe_xdp_setup

The ixgbe driver currently generates a NULL pointer dereference with

some machine (online cpus < 63). This is due to the fact that the

maximum value of num_xdp_queues is nr_cpu_ids. Code is in

"ixgbe_set_rss_queues"".

Here's how the problem repeats itself:

Some machine (online cpus < 63), And user set num_queues to 63 through

ethtool. Code is in the "ixgbe_set_channels",

adapter->ring_feature[RING_F_FDIR].limit = count;

It becomes 63.

When user use xdp, "ixgbe_set_rss_queues" will set queues num.

adapter->num_rx_queues = rss_i;

adapter->num_tx_queues = rss_i;

adapter->num_xdp_queues = ixgbe_xdp_queues(adapter);

And rss_i's value is from

f = &adapter->ring_feature[RING_F_FDIR];

rss_i = f->indices = f->limit;

So "num_rx_queues" > "num_xdp_queues", when run to "ixgbe_xdp_setup",

for (i = 0; i < adapter->num_rx_queues; i++)

if (adapter->xdp_ring[i]->xsk_umem)

It leads to panic.

Call trace:

[exception RIP: ixgbe_xdp+368]

RIP: ffffffffc02a76a0 RSP: ffff9fe16202f8d0 RFLAGS: 00010297

RAX: 0000000000000000 RBX: 0000000000000020 RCX: 0000000000000000

RDX: 0000000000000000 RSI: 000000000000001c RDI: ffffffffa94ead90

RBP: ffff92f8f24c0c18 R8: 0000000000000000 R9: 0000000000000000

R10: ffff9fe16202f830 R11: 0000000000000000 R12: ffff92f8f24c0000

R13: ffff9fe16202fc01 R14: 000000000000000a R15: ffffffffc02a7530

ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018

7 [ffff9fe16202f8f0] dev_xdp_install at ffffffffa89fbbcc

8 [ffff9fe16202f920] dev_change_xdp_fd at ffffffffa8a08808

9 [ffff9fe16202f960] do_setlink at ffffffffa8a20235

10 [ffff9fe16202fa88] rtnl_setlink at ffffffffa8a20384

11 [ffff9fe16202fc78] rtnetlink_rcv_msg at ffffffffa8a1a8dd

12 [ffff9fe16202fcf0] netlink_rcv_skb at ffffffffa8a717eb

13 [ffff9fe16202fd40] netlink_unicast at ffffffffa8a70f88

14 [ffff9fe16202fd80] netlink_sendmsg at ffffffffa8a71319

15 [ffff9fe16202fdf0] sock_sendmsg at ffffffffa89df290

16 [ffff9fe16202fe08] __sys_sendto at ffffffffa89e19c8

17 [ffff9fe16202ff30] __x64_sys_sendto at ffffffffa89e1a64

18 [ffff9fe16202ff38] do_syscall_64 at ffffffffa84042b9

19 [ffff9fe16202ff50] entry_SYSCALL_64_after_hwframe at ffffffffa8c0008c

So I fix ixgbe_max_channels so that it will not allow a setting of queues

to be higher than the num_online_cpus(). And when run to ixgbe_xdp_setup,

take the smaller value of num_rx_queues and num_xdp_queues.