Drivers: hv: avoid vfree() on crash

commit a9f61ca upstream. When we crash from NMI context (e.g. after NMI injection from host when 'sysctl -w kernel.unknown_nmi_panic=1' is set) we hit kernel BUG at mm/vmalloc.c:1530! as vfree() is denied. While the issue could be solved with in_nmi() check instead I opted for skipping vfree on all sorts of crashes to reduce the amount of work which can cause consequent crashes. We don't really need to free anything on crash. [js] no tsc and kexec in 3.12 yet Signed-off-by: Vitaly Kuznetsov <[email protected]> Signed-off-by: K. Y. Srinivasan <[email protected]> Cc: Sumit Semwal <[email protected]> Signed-off-by: Jiri Slaby <[email protected]> Signed-off-by: Willy Tarreau <[email protected]>
hardkernel · Jun 7, 2017 · 9391c80 · 9391c80
1 parent 801c8a0
commit 9391c80
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Showing 3 changed files with 6 additions and 5 deletions.
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
@@ -193,7 +193,7 @@ int hv_init(void)
  *
  * This routine is called normally during driver unloading or exiting.
  */
-void hv_cleanup(void)
+void hv_cleanup(bool crash)
 {
 	union hv_x64_msr_hypercall_contents hypercall_msr;
 
@@ -203,7 +203,8 @@ void hv_cleanup(void)
 	if (hv_context.hypercall_page) {
 		hypercall_msr.as_uint64 = 0;
 		wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
-		vfree(hv_context.hypercall_page);
+		if (!crash)
+			vfree(hv_context.hypercall_page);
 		hv_context.hypercall_page = NULL;
 	}
 }

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
@@ -519,7 +519,7 @@ extern struct hv_context hv_context;
 
 extern int hv_init(void);
 
-extern void hv_cleanup(void);
+extern void hv_cleanup(bool crash);
 
 extern int hv_post_message(union hv_connection_id connection_id,
 			 enum hv_message_type message_type,

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
@@ -618,7 +618,7 @@ static int vmbus_bus_init(int irq)
 	bus_unregister(&hv_bus);
 
 err_cleanup:
-	hv_cleanup();
+	hv_cleanup(false);
 
 	return ret;
 }
@@ -841,7 +841,7 @@ static void __exit vmbus_exit(void)
 	free_irq(irq, hv_acpi_dev);
 	vmbus_free_channels();
 	bus_unregister(&hv_bus);
-	hv_cleanup();
+	hv_cleanup(false);
 	acpi_bus_unregister_driver(&vmbus_acpi_driver);
 	hv_cpu_hotplug_quirk(false);
 }