2024-12-28 09:46:24
Linux
PUBLISHED
In the Linux kernel, the following vulnerability has been resolved:
ipv6: Fix soft lockups in fib6_select_path under high next hop churn
Soft lockups have been observed on a cluster of Linux-based edge routers
located in a highly dynamic environment. Using the `bird` service, these
routers continuously update BGP-advertised routes due to frequently
changing nexthop destinations, while also managing significant IPv6
traffic. The lockups occur during the traversal of the multipath
circular linked-list in the `fib6_select_path` function, particularly
while iterating through the siblings in the list. The issue typically
arises when the nodes of the linked list are unexpectedly deleted
concurrently on a different core—indicated by their next and
previous elements pointing back to the node itself and their reference
count dropping to zero. This results in an infinite loop, leading to a
soft lockup that triggers a system panic via the watchdog timer.
Apply RCU primitives in the problematic code sections to resolve the
issue. Where necessary, update the references to fib6_siblings to
annotate or use the RCU APIs.
Include a test script that reproduces the issue. The script
periodically updates the routing table while generating a heavy load
of outgoing IPv6 traffic through multiple iperf3 clients. It
consistently induces infinite soft lockups within a couple of minutes.
Kernel log:
0 [ffffbd13003e8d30] machine_kexec at ffffffff8ceaf3eb
1 [ffffbd13003e8d90] __crash_kexec at ffffffff8d0120e3
2 [ffffbd13003e8e58] panic at ffffffff8cef65d4
3 [ffffbd13003e8ed8] watchdog_timer_fn at ffffffff8d05cb03
4 [ffffbd13003e8f08] __hrtimer_run_queues at ffffffff8cfec62f
5 [ffffbd13003e8f70] hrtimer_interrupt at ffffffff8cfed756
6 [ffffbd13003e8fd0] __sysvec_apic_timer_interrupt at ffffffff8cea01af
7 [ffffbd13003e8ff0] sysvec_apic_timer_interrupt at ffffffff8df1b83d
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