CVE-2026-93226

Summary

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

ipv6: use RCU iterator to dump route exceptions

rt6_nh_dump_exceptions() uses hlist_for_each_entry() to iterate over RCU-protected exception lists. The caller holds rcu_read_lock(), but does not hold rt6_exception_lock, so rt6_insert_exception() can concurrently add an entry with hlist_add_head_rcu().

KCSAN reports this race (irrelevant details omitted):

================================================================== BUG: KCSAN: data-race in rt6_insert_exception / rt6_nh_dump_exceptions

write (marked) to 0xffff8a7c44c59620 of 8 bytes by interrupt on cpu 5: rt6_insert_exception+0x3bb/0x760 __ip6_rt_update_pmtu+0x4fe/0x750 ip6_sk_update_pmtu+0x19a/0x3b0 udpv6_err+0x3ff/0x800 icmpv6_notify+0x1e1/0x440 icmpv6_rcv+0x8c0/0xab0 ip6_protocol_deliver_rcu+0x616/0x840 ip6_input_finish+0xb9/0x160 … entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8a7c44c59620 of 8 bytes by task 549 on cpu 14: rt6_nh_dump_exceptions+0xb3/0x260 rt6_dump_route+0x53e/0x5f0 fib6_dump_node+0x6d/0xf0 fib6_walk_continue+0x290/0x2d0 fib6_dump_table+0x28d/0x360 inet6_dump_fib+0x37d/0x620 rtnl_dumpit+0x7b/0xd0 netlink_dump+0x3ae/0x7e0 … entry_SYSCALL_64_after_hwframe+0x77/0x7f

4 locks held by dumper/549: … #1: (rcu_read_lock){….}-{1:3}, at: inet6_dump_fib+0x88/0x620 #2: (&tb->tb6_lock){+.-.}-{3:3}, at: fib6_dump_table+0x1e9/0x360 #3: (rcu_read_lock){….}-{1:3}, at: rt6_dump_route+0x483/0x5f0

value changed: 0xffff8a7c44e05700 -> 0xffff8a7c45d60100

Reported by Kernel Concurrency Sanitizer on: CPU: 14 UID: 0 PID: 549 Comm: dumper Not tainted 7.2.0-rc7-virtme #38 PREEMPT(lazy) …

Use hlist_for_each_entry_rcu() to safely iterate over the exception list.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/dffbfb3117138e8e0e09d05f507bd36ca1f696e5
• https://git.kernel.org/stable/c/6bd3f94ed858f2d072627546b4cdf712b0f8ea88
• https://git.kernel.org/stable/c/9c6be625e1a7258e845d6193b3b6b084a00f8e9e
• https://git.kernel.org/stable/c/3665abc3d2ae8a78cb67f858e848481432ec75db
• https://git.kernel.org/stable/c/eda56ee17713f9dd834b922f7dbfa2e25fa6358c
• https://git.kernel.org/stable/c/a602cd128d17a793e12888edc8eda85821ede7e1
• https://git.kernel.org/stable/c/f6b1b15848fd91fe122dac0d19d3d666e35075b6
• https://git.kernel.org/stable/c/47cdab0d51aaa9bd85f8e4904585bd5bd4df4488

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