Linux Linux Kernel Vulnerability Rated 8.8 CVSS

Status: UPDATED  |  Advisory ID: CVE-2026-74691

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

net: thunderbolt: Tear down DMA paths before stopping the rings

tbnet_tear_down() stops both rings and frees their frame buffers before

calling tb_xdomain_disable_paths(). tb_ring_stop() zeroes the ring's

descriptor base and tbnet_free_buffers() unmaps and frees the pages the

frames sit in, so by the time __tb_path_deactivate_hop() polls the hop's

'pending' bit, anything still in flight has nowhere to drain to.

The teardown sequence has been in this order since the driver was added.

The setup path has not: commit ff7cd07f3064 ("net: thunderbolt: Enable

DMA paths only after rings are enabled") moved the path enable to the end

of tbnet_connected_work() and documented why:

/* Both logins successful so enable the rings, high-speed DMA

* paths and start the network device queue.

*

* Note we enable the DMA paths last to make sure we have primed

* the Rx ring before any incoming packets are allowed to

* arrive.

*/

Teardown was never updated to match, so the rings and the paths now come

down in the same order they go up instead of in reverse.

On an ASMedia ASM4242 host router the 'pending' bit then never clears:

every teardown burns the full 500 ms timeout and

__tb_path_deactivate_hop() returns -ETIMEDOUT. Raising the timeout to

5 s does not help, so the hop is not slow to drain, it never drains

at all.

The failure is invisible above the thunderbolt core.

__tb_path_deactivate_hops() is void and only calls tb_port_warn();

tb_path_deactivate(), tb_tunnel_deactivate() and

__tb_disconnect_xdomain_paths() are void as well, and

tb_disconnect_xdomain_paths() ends in an unconditional "return 0". So

tb_xdomain_disable_paths() reports success and the netdev_warn() below

it never fires. Repeated teardowns eventually take the XDomain control

channel down, after which the peer node is gone and only a power cycle

brings the controller back.

Deactivating the paths first fixes it. Measured with kretprobes on a

stock v6.17 tree with no other patches applied, on a link that was up

and had just carried traffic:

before: __tb_path_deactivate_hop() returns 0 for the first hop, then

-ETIMEDOUT for the second 500335 us later

after: 0 for both, 525 us apart

Alternating the two orderings ABBA over three load levels, four

teardowns per arm: every teardown failed before the change (21 of 21

that ran), none failed after (0 of 24). The before arms ran short

because the link died partway through. The same split shows up when

the interface is enslaved to a bond instead of just brought down, which

is how I ran into this in the first place. Throughput and latency after

the change are unchanged.

Hosts whose routers drain the hop despite the stale descriptor base see

no functional difference, since the paths end up deactivated either way. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References