svn commit: r368513 - head/sys/dev/hyperv/vmbus

[Bradley T. Hughes]

Author: bhughes (ports committer)
Date: Thu Dec 10 13:11:52 2020
New Revision: 368513
URL: https://svnweb.freebsd.org/changeset/base/368513

Log:
  hyperv/vmbus: avoid crash, panic if vbe fb info is missing
  
  Do not assume that VBE framebuffer metadata can be used. Like with the
  EFI fb metadata, it may be null, so we should take care not to
  dereference the null vbefb pointer. This avoids a panic when booting
  -CURRENT on a gen1 VM in Azure.
  
  Approved by:	tsoome
  Sponsored by:	Miles AS
  Differential Revision:	https://reviews.freebsd.org/D27533

Modified:
  head/sys/dev/hyperv/vmbus/vmbus.c

Modified: head/sys/dev/hyperv/vmbus/vmbus.c
==============================================================================
--- head/sys/dev/hyperv/vmbus/vmbus.c	Thu Dec 10 13:08:06 2020	(r368512)
+++ head/sys/dev/hyperv/vmbus/vmbus.c	Thu Dec 10 13:11:52 2020	(r368513)
@@ -1361,35 +1361,33 @@ vmbus_fb_mmio_res(device_t dev)
 		kmdp = preload_search_by_type("elf64 kernel");
 	efifb = (struct efi_fb *)preload_search_info(kmdp,
 	    MODINFO_METADATA | MODINFOMD_EFI_FB);
-	if (efifb == NULL) {
-		vbefb = (struct vbe_fb *)preload_search_info(kmdp,
-		    MODINFO_METADATA | MODINFOMD_VBE_FB);
+	vbefb = (struct vbe_fb *)preload_search_info(kmdp,
+	    MODINFO_METADATA | MODINFOMD_VBE_FB);
+	if (efifb != NULL) {
+		fb_start = efifb->fb_addr;
+		fb_end = efifb->fb_addr + efifb->fb_size;
+		fb_count = efifb->fb_size;
+		fb_height = efifb->fb_height;
+		fb_width = efifb->fb_width;
+	} else if (vbefb != NULL) {
 		fb_start = vbefb->fb_addr;
 		fb_end = vbefb->fb_addr + vbefb->fb_size;
 		fb_count = vbefb->fb_size;
 		fb_height = vbefb->fb_height;
 		fb_width = vbefb->fb_width;
 	} else {
-		fb_start = efifb->fb_addr;
-		fb_end = efifb->fb_addr + efifb->fb_size;
-		fb_count = efifb->fb_size;
-		fb_height = efifb->fb_height;
-		fb_width = efifb->fb_width;
-	}
-
-	if (fb_start == 0) {
 		if (bootverbose)
 			device_printf(dev,
 			    "no preloaded kernel fb information\n");
 		/* We are on Gen1 VM, just return. */
 		return;
-	} else {
-		if (bootverbose)
-			device_printf(dev,
-			    "fb: fb_addr: %#jx, size: %#jx, "
-			    "actual size needed: 0x%x\n",
-			    fb_start, fb_count, fb_height * fb_width);
 	}
+	
+	if (bootverbose)
+		device_printf(dev,
+		    "fb: fb_addr: %#jx, size: %#jx, "
+		    "actual size needed: 0x%x\n",
+		    fb_start, fb_count, fb_height * fb_width);
 
 	hv_fb_res = pcib_host_res_alloc(&sc->vmbus_mmio_res, dev,
 	    SYS_RES_MEMORY, &rid, fb_start, fb_end, fb_count,