xen/x86/vpmu: Zero struct pt_regs before calling into sample handling code

Otherwise we may leak kernel stack for events that sample user
registers.

Reported-by: Mark Rutland <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Signed-off-by: Boris Ostrovsky <[email protected]>
Cc: [email protected]

Author: Boris Ostrovsky

arch/x86/xen/pmu.c

@@ -478,7 +478,7 @@ static void xen_convert_regs(const struct xen_pmu_regs *xen_regs,
 irqreturn_t xen_pmu_irq_handler(int irq, void *dev_id)
 {
 	int err, ret = IRQ_NONE;
-	struct pt_regs regs;
+	struct pt_regs regs = {0};
 	const struct xen_pmu_data *xenpmu_data = get_xenpmu_data();
 	uint8_t xenpmu_flags = get_xenpmu_flags();