CVE-2025-39767 LoongArch: Optimize module load time by optimizing PLT/GOT counting
A local attacker can cause a soft deadlock and system hang by loading specific kernel modules under certain debug configurations.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39767?
CVE-2025-39767 is a medium-severity denial of service vulnerability in Linux kernel, published on 11 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
LoongArch: Optimize module load time by optimizing PLT/GOT counting
When enabling CONFIG_KASAN, CONFIG_PREEMPT_VOLUNTARY_BUILD and CONFIG_PREEMPT_VOLUNTARY at the same time, there will be soft deadlock, the relevant logs are as follows:
rcu: INFO: rcu_sched self-detected stall on CPU ... Call Trace: [<900000000024f9e4>] show_stack+0x5c/0x180 [<90000000002482f4>] dump_stack_lvl+0x94/0xbc [<9000000000224544>] rcu_dump_cpu_stacks+0x1fc/0x280 [<900000000037ac80>] rcu_sched_clock_irq+0x720/0xf88 [<9000000000396c34>] update_process_times+0xb4/0x150 [<90000000003b2474>] tick_nohz_handler+0xf4/0x250 [<9000000000397e28>] __hrtimer_run_queues+0x1d0/0x428 [<9000000000399b2c>] hrtimer_interrupt+0x214/0x538 [<9000000000253634>] constant_timer_interrupt+0x64/0x80 [<9000000000349938>] __handle_irq_event_percpu+0x78/0x1a0 [<9000000000349a78>] handle_irq_event_percpu+0x18/0x88 [<9000000000354c00>] handle_percpu_irq+0x90/0xf0 [<9000000000348c74>] handle_irq_desc+0x94/0xb8 [<9000000001012b28>] handle_cpu_irq+0x68/0xa0 [<9000000001def8c0>] handle_loongarch_irq+0x30/0x48 [<9000000001def958>] do_vint+0x80/0xd0 [<9000000000268a0c>] kasan_mem_to_shadow.part.0+0x2c/0x2a0 [<90000000006344f4>] __asan_load8+0x4c/0x120 [<900000000025c0d0>] module_frob_arch_sections+0x5c8/0x6b8 [<90000000003895f0>] load_module+0x9e0/0x2958 [<900000000038b770>] __do_sys_init_module+0x208/0x2d0 [<9000000001df0c34>] do_syscall+0x94/0x190 [<900000000024d6fc>] handle_syscall+0xbc/0x158
After analysis, this is because the slow speed of loading the amdgpu module leads to the long time occupation of the cpu and then the soft deadlock.
When loading a module, module_frob_arch_sections() tries to figure out the number of PLTs/GOTs that will be needed to handle all the RELAs. It will call the count_max_entries() to find in an out-of-order date which counting algorithm has O(n^2) complexity.
To make it faster, we sort the relocation list by info and addend. That way, to check for a duplicate relocation, it just needs to compare with the previous entry. This reduces the complexity of the algorithm to O(n log n), as done in commit d4e0340919fb ("arm64/module: Optimize module load time by optimizing PLT counting"). This gives sinificant reduction in module load time for modules with large number of relocations.
After applying this patch, the soft deadlock problem has been solved, and the kernel starts normally without "Call Trace".
Using the default configuration to test some modules, the results are as follows:
Module Size ip_tables 36K fat 143K radeon 2.5MB amdgpu 16MB
Without this patch: Module Module load time (ms) Count(PLTs/GOTs) ip_tables 18 59/6 fat 0 162/14 radeon 54 1221/84 amdgpu 1411 4525/1098
With this patch: Module Module load time (ms) Count(PLTs/GOTs) ip_tables 18 59/6 fat 0 162/14 radeon 22 1221/84 amdgpu 45 4525/1098
Weakness: CWE-667
Which versions are affected by CVE-2025-39767?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-39767?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-39767 being exploited?
There is no known exploitation of CVE-2025-39767 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-67193, BELL-CVE-2025-39767, DEBIAN-CVE-2025-39767, GHSA-2pv7-jfgv-x3fr, ROOT-OS-DEBIAN-12-CVE-2025-39767, ROOT-OS-DEBIAN-13-CVE-2025-39767 and 1 more.