[PATCH] mshv: bounds-check cpu index in vtl mmap fault handler

[Yi Xie]

cpu is taken from pgoff & 0xffff.  cpu_online() does not reject cpu >=
nr_cpu_ids, and per_cpu_ptr() can then walk off __per_cpu_offset.

Signed-off-by: Yi Xie <xieyi@xxxxxxxxxx>
---
 drivers/hv/mshv_vtl_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
index 0d3d4161974f..fc50c44ac1bd 100644
--- a/drivers/hv/mshv_vtl_main.c
+++ b/drivers/hv/mshv_vtl_main.c
@@ -801,7 +801,7 @@ static vm_fault_t mshv_vtl_fault(struct vm_fault *vmf)
 	int cpu = vmf->pgoff & MSHV_PG_OFF_CPU_MASK;
 	int real_off = vmf->pgoff >> MSHV_REAL_OFF_SHIFT;
 
-	if (!cpu_online(cpu))
+	if (cpu >= nr_cpu_ids || !cpu_online(cpu))
 		return VM_FAULT_SIGBUS;
 	/*
 	 * CPU Hotplug is not supported in VTL2 in OpenHCL, where this kernel driver exists.
-- 
2.34.1