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hyperv/vmbus: avoid crash, panic if vbe fb info is missing

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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
This commit is contained in:
Bradley T. Hughes 2020-12-10 13:11:52 +00:00
parent 6580cc162d
commit c05b5848f1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=368513
1 changed files with 15 additions and 17 deletions
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32
sys/dev/hyperv/vmbus/vmbus.c
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@ -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,