CVE-2025-38727

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

netlink: avoid infinite retry looping in netlink_unicast()

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

rmem < READ_ONCE(sk->sk_rcvbuf)

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

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

The checks dont 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: 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

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

References

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