CVE-2025-38407 riscv: cpu_ops_sbi: Use static array for boot_data

Medium 5.5 Published 25 Jul 2025 Updated 11 May 2026

A kernel bug causes a hang during secondary CPU boot on RISC-V systems with NUMA enabled, leading to denial of service.

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-2025-38407?

CVE-2025-38407 is a medium-severity vulnerability in Linux kernel, published on 25 Jul 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:

riscv: cpu_ops_sbi: Use static array for boot_data

Since commit 6b9f29b81b15 ("riscv: Enable pcpu page first chunk allocator"), if NUMA is enabled, the page percpu allocator may be used on very sparse configurations, or when requested on boot with percpu_alloc=page.

In that case, percpu data gets put in the vmalloc area. However, sbi_hsm_hart_start() needs the physical address of a sbi_hart_boot_data, and simply assumes that __pa() would work. This causes the just started hart to immediately access an invalid address and hang.

Fortunately, struct sbi_hart_boot_data is not too large, so we can simply allocate an array for boot_data statically, putting it in the kernel image.

This fixes NUMA=y SMP boot on Sophgo SG2042.

To reproduce on QEMU: Set CONFIG_NUMA=y and CONFIG_DEBUG_VIRTUAL=y, then run with:

qemu-system-riscv64 -M virt -smp 2 -nographic \ -kernel arch/riscv/boot/Image \ -append "percpu_alloc=page"

Kernel output:

[ 0.000000] Booting Linux on hartid 0 [ 0.000000] Linux version 6.16.0-rc1 (dram@sakuya) (riscv64-unknown-linux-gnu-gcc (GCC) 14.2.1 20250322, GNU ld (GNU Binutils) 2.44) #11 SMP Tue Jun 24 14:56:22 CST 2025 ... [ 0.000000] percpu: 28 4K pages/cpu s85784 r8192 d20712 ... [ 0.083192] smp: Bringing up secondary CPUs ... [ 0.086722] ------------[ cut here ]------------ [ 0.086849] virt_to_phys used for non-linear address: (____ptrval____) (0xff2000000001d080) [ 0.088001] WARNING: CPU: 0 PID: 1 at arch/riscv/mm/physaddr.c:14 __virt_to_phys+0xae/0xe8 [ 0.088376] Modules linked in: [ 0.088656] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.16.0-rc1 #11 NONE [ 0.088833] Hardware name: riscv-virtio,qemu (DT) [ 0.088948] epc : __virt_to_phys+0xae/0xe8 [ 0.089001] ra : __virt_to_phys+0xae/0xe8 [ 0.089037] epc : ffffffff80021eaa ra : ffffffff80021eaa sp : ff2000000004bbc0 [ 0.089057] gp : ffffffff817f49c0 tp : ff60000001d60000 t0 : 5f6f745f74726976 [ 0.089076] t1 : 0000000000000076 t2 : 705f6f745f747269 s0 : ff2000000004bbe0 [ 0.089095] s1 : ff2000000001d080 a0 : 0000000000000000 a1 : 0000000000000000 [ 0.089113] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 [ 0.089131] a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000 [ 0.089155] s2 : ffffffff8130dc00 s3 : 0000000000000001 s4 : 0000000000000001 [ 0.089174] s5 : ffffffff8185eff8 s6 : ff2000007f1eb000 s7 : ffffffff8002a2ec [ 0.089193] s8 : 0000000000000001 s9 : 0000000000000001 s10: 0000000000000000 [ 0.089211] s11: 0000000000000000 t3 : ffffffff8180a9f7 t4 : ffffffff8180a9f7 [ 0.089960] t5 : ffffffff8180a9f8 t6 : ff2000000004b9d8 [ 0.089984] status: 0000000200000120 badaddr: ffffffff80021eaa cause: 0000000000000003 [ 0.090101] [<ffffffff80021eaa>] __virt_to_phys+0xae/0xe8 [ 0.090228] [<ffffffff8001d796>] sbi_cpu_start+0x6e/0xe8 [ 0.090247] [<ffffffff8001a5da>] __cpu_up+0x1e/0x8c [ 0.090260] [<ffffffff8002a32e>] bringup_cpu+0x42/0x258 [ 0.090277] [<ffffffff8002914c>] cpuhp_invoke_callback+0xe0/0x40c [ 0.090292] [<ffffffff800294e0>] __cpuhp_invoke_callback_range+0x68/0xfc [ 0.090320] [<ffffffff8002a96a>] _cpu_up+0x11a/0x244 [ 0.090334] [<ffffffff8002aae6>] cpu_up+0x52/0x90 [ 0.090384] [<ffffffff80c09350>] bringup_nonboot_cpus+0x78/0x118 [ 0.090411] [<ffffffff80c11060>] smp_init+0x34/0xb8 [ 0.090425] [<ffffffff80c01220>] kernel_init_freeable+0x148/0x2e4 [ 0.090442] [<ffffffff80b83802>] kernel_init+0x1e/0x14c [ 0.090455] [<ffffffff800124ca>] ret_from_fork_kernel+0xe/0xf0 [ 0.090471] [<ffffffff80b8d9c2>] ret_from_fork_kernel_asm+0x16/0x18 [ 0.090560] ---[ end trace 0000000000000000 ]--- [ 1.179875] CPU1: failed to come online [ 1.190324] smp: Brought up 1 node, 1 CPU

Which versions are affected by CVE-2025-38407?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-38407?

Apply the vendor's patch.

Is CVE-2025-38407 being exploited?

There is no known exploitation of CVE-2025-38407 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as BELL-CVE-2025-38407, DEBIAN-CVE-2025-38407, GHSA-qq4v-pr8w-v8hg, ROOT-OS-UBUNTU-2404-CVE-2025-38407, UBUNTU-CVE-2025-38407.