x86/hyperv: Fix error pointer dereference

The function idle_thread_get() can return an error pointer and is not
checked for it. Add check for error pointer.

Detected by Smatch:
arch/x86/hyperv/hv_vtl.c:126 hv_vtl_bringup_vcpu() error:
'idle' dereferencing possible ERR_PTR()

Fixes: 2b4b90e053a29 ("x86/hyperv: Use per cpu initial stack for vtl context")
Signed-off-by: Ethan Tidmore <ethantidmore06@gmail.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index c0edaed..9b6a9bc 100644 (file)
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -110,7 +110,7 @@ static void hv_vtl_ap_entry(void)
 
 static int hv_vtl_bringup_vcpu(u32 target_vp_index, int cpu, u64 eip_ignored)
 {
-       u64 status;
+       u64 status, rsp, rip;
        int ret = 0;
        struct hv_enable_vp_vtl *input;
        unsigned long irq_flags;
@@ -123,9 +123,11 @@ static int hv_vtl_bringup_vcpu(u32 target_vp_index, int cpu, u64 eip_ignored)
        struct desc_struct *gdt;
 
        struct task_struct *idle = idle_thread_get(cpu);
-       u64 rsp = (unsigned long)idle->thread.sp;
+       if (IS_ERR(idle))
+               return PTR_ERR(idle);
 
-       u64 rip = (u64)&hv_vtl_ap_entry;
+       rsp = (unsigned long)idle->thread.sp;
+       rip = (u64)&hv_vtl_ap_entry;
 
        native_store_gdt(&gdt_ptr);
        store_idt(&idt_ptr);