On 2026/7/9 下午5:33, Thomas Huth wrote:
On 09/07/2026 11.08, Bibo Mao wrote:
On 2026/7/1 下午2:54, Song Gao wrote:
Validate guest-controlled cpu_num before using it to index the cpu[]
array
or pass to async_run_on_cpu(). Without this check, a malicious guest can
trigger a NULL pointer dereference in async_run_on_cpu() and an
out-of-bounds array access in qemu_set_irq(), causing host crash.
Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3616
Fixes: 0d148eaf5a3e ("hw/loongarch: Implement dintc set irq")
Reported-by: Thomas Huth <[email protected]>
Signed-off-by: Song Gao <[email protected]>
---
hw/intc/loongarch_dintc.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/hw/intc/loongarch_dintc.c b/hw/intc/loongarch_dintc.c
index c877a8003b..e40292887c 100644
--- a/hw/intc/loongarch_dintc.c
+++ b/hw/intc/loongarch_dintc.c
@@ -19,6 +19,7 @@
#include "target/loongarch/cpu.h"
#include "qemu/error-report.h"
#include "system/hw_accel.h"
+#include "qemu/log.h"
/* msg addr field */
FIELD(MSG_ADDR, IRQ_NUM, 4, 8)
@@ -52,7 +53,19 @@ static void loongarch_dintc_mem_write(void
*opaque, hwaddr addr,
CPUState *cs;
cpu_num = FIELD_EX64(msg_addr, MSG_ADDR, CPU_NUM);
+
+ /* Validate cpu_num against the configured number of CPUs */
+ if (cpu_num >= s->num_cpu) {
+ qemu_log_mask(LOG_GUEST_ERROR,
+ "loongarch-dintc: invalid cpu number%d\n",
cpu_num);
+ return;
+ }
Here cpu_num decoded from MSG_ADDR is physical CPU ID, I think that it
is not meaningful to compare it with s->num_cpu.
Later in this function, cpu_num is used to index into the s->cpu[] array:
qemu_set_irq(s->cpu[cpu_num].parent_irq, 1);
and s->cpu is allocated like this in the realize function:
s->num_cpu = id_list->len;
s->cpu = g_new(DINTCCore, s->num_cpu);
So the new check here looks valid for me, at least right now. Or what
else would you suggest here?
I prefer separate function dintc_cpu_by_arch_id(), this piece of code is
not tested.
+static int loongarch_dintc_cmp(const void *a, const void *b)
+{
+ DINTCCore *dintc_a = (DINTCCore *)a;
+ DINTCCore *dintc_b = (DINTCCore *)b;
+
+ return dintc_a->arch_id - dintc_a->arch_id;
+}
+
+static int dintc_cpu_by_arch_id(LoongArchDINTCState *s,
+ int64_t arch_id, int *index, CPUState
**pcs)
+{
+ DINTCCore dintc, *found;
+
+ dintc.arch_id = arch_id;
+ found = bsearch(&dintc, s->cpu, s->num_cpu, sizeof(DINTCCore),
+ loongarch_dintc_cmp);
+ if (found && found->cpu) {
+ if (index) {
+ *index = found - s->cpu;
+ }
+
+ if (pcs) {
+ *pcs = found->cpu;
+ }
+
+ return MEMTX_OK;
+ }
+
+ return MEMTX_ERROR;
+}
+
static void loongarch_dintc_mem_write(void *opaque, hwaddr addr,
uint64_t val, unsigned size)
{
- int irq_num, cpu_num = 0;
+ int irq_num, cpu_num, ret;
LoongArchDINTCState *s = LOONGARCH_DINTC(opaque);
uint64_t msg_addr = addr + VIRT_DINTC_BASE;
CPUState *cs;
+ uint32_t cpuid;
- cpu_num = FIELD_EX64(msg_addr, MSG_ADDR, CPU_NUM);
- cs = cpu_by_arch_id(cpu_num);
+ cpuid = FIELD_EX64(msg_addr, MSG_ADDR, CPU_NUM);
irq_num = FIELD_EX64(msg_addr, MSG_ADDR, IRQ_NUM);
+ ret = dintc_cpu_by_arch_id(s, cpuid, &cpu_num, &cs);
+ if (ret != MEMTX_OK || cpu_num >= ipi->num_cpu) {
+ qemu_log_mask(LOG_GUEST_ERROR,
+ "loongarch-dintc: no CPU for arch_id %d\n", cpuid);
+ return;
+ }
async_run_on_cpu(cs, do_set_vcpu_dintc_irq,
RUN_ON_CPU_HOST_INT(irq_num));
Regards
Bibo Mao
Thomas
cs = cpu_by_arch_id(cpu_num);
This is ok to use cpu_by_arch_id now, in later when CPU hotplug is
support with dintc, there should be self CPU search logic like ipi
irqchip.
Regards
Bibo Mao
+ if (!cs) {
+ qemu_log_mask(LOG_GUEST_ERROR,
+ "loongarch-dintc: no CPU for arch_id %d\n",
cpu_num);
+ return;
+ }
irq_num = FIELD_EX64(msg_addr, MSG_ADDR, IRQ_NUM);
async_run_on_cpu(cs, do_set_vcpu_dintc_irq,
