CVE-2025-38727

Summary

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

netlink: avoid infinite retry looping in netlink_unicast()

netlink_attachskb() checks for the socket's read memory allocation constraints. Firstly, it has:

rmem < READ_ONCE(sk->sk_rcvbuf)

to check if the just increased rmem value fits into the socket's receive buffer. If not, it proceeds and tries to wait for the memory under:

rmem + skb->truesize > READ_ONCE(sk->sk_rcvbuf)

The checks don't cover the case when skb->truesize + sk->sk_rmem_alloc is equal to sk->sk_rcvbuf. Thus the function neither successfully accepts these conditions, nor manages to reschedule the task - and is called in retry loop for indefinite time which is caught as:

rcu: INFO: rcu_sched self-detected stall on CPU rcu: 0-….: (25999 ticks this GP) idle=ef2/1/0x4000000000000000 softirq=262269/262269 fqs=6212 (t=26000 jiffies g=230833 q=259957) NMI backtrace for cpu 0 CPU: 0 PID: 22 Comm: kauditd Not tainted 5.10.240 #68 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc42 04/01/2014 Call Trace: <IRQ> dump_stack lib/dump_stack.c:120 nmi_cpu_backtrace.cold lib/nmi_backtrace.c:105 nmi_trigger_cpumask_backtrace lib/nmi_backtrace.c:62 rcu_dump_cpu_stacks kernel/rcu/tree_stall.h:335 rcu_sched_clock_irq.cold kernel/rcu/tree.c:2590 update_process_times kernel/time/timer.c:1953 tick_sched_handle kernel/time/tick-sched.c:227 tick_sched_timer kernel/time/tick-sched.c:1399 __hrtimer_run_queues kernel/time/hrtimer.c:1652 hrtimer_interrupt kernel/time/hrtimer.c:1717 __sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1113 asm_call_irq_on_stack arch/x86/entry/entry_64.S:808 </IRQ>

netlink_attachskb net/netlink/af_netlink.c:1234 netlink_unicast net/netlink/af_netlink.c:1349 kauditd_send_queue kernel/audit.c:776 kauditd_thread kernel/audit.c:897 kthread kernel/kthread.c:328 ret_from_fork arch/x86/entry/entry_64.S:304

Restore the original behavior of the check which commit in Fixes accidentally missed when restructuring the code.

Found by Linux Verification Center (linuxtesting.org).

Affected Software

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
• https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html

Additional References

• https://cert-portal.siemens.com/productcert/html/ssa-082556.html
• https://cert-portal.siemens.com/productcert/html/ssa-032379.html

References

• https://git.kernel.org/stable/c/47d49fd07f86d1f55ea1083287303d237e9e0922
• https://git.kernel.org/stable/c/6bee383ff83352a693d03efdf27cdd80742f71b2
• https://git.kernel.org/stable/c/f324959ad47e62e3cadaffa65d3cff790fb48529
• https://git.kernel.org/stable/c/d42b71a34f6b8a2d5c53df81169b03b8d8b5cf4e
• https://git.kernel.org/stable/c/346c820ef5135cf062fa3473da955ef8c5fb6929
• https://git.kernel.org/stable/c/44ddd7b1ae0b7edb2c832eb16798c827a05e58f0
• https://git.kernel.org/stable/c/78fcd69d55c5f11d7694c547eca767a1cfd38ec4
• https://git.kernel.org/stable/c/e8edc7de688791a337c068693f22e8d8b869df71
• https://git.kernel.org/stable/c/759dfc7d04bab1b0b86113f1164dc1fec192b859

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