nouveau: Fix crash when pci_ram_rom() returns a size of 0

From b15b244d6e6e20964bd4b85306722cb60c3c0809 Mon Sep 17 00:00:00 2001
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Mon, 2 Apr 2012 13:28:18 +1000
Subject:

Under some circumstances, pci_map_rom() can return a valid mapping
but a size of 0 (if it cannot find an image in the header).

This causes nouveau to try to kmalloc() a 0 sized pointer and
dereference it, which crashes.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/nouveau/nouveau_bios.c b/drivers/gpu/drm/nouveau/nouveau_bios.c
index 637afe7..80963d0 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_bios.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bios.c
@@ -177,14 +177,15 @@ bios_shadow_pci(struct nvbios *bios)
 
        if (!pci_enable_rom(pdev)) {
                void __iomem *rom = pci_map_rom(pdev, &length);
-               if (rom) {
+               if (rom && length) {
                        bios->data = kmalloc(length, GFP_KERNEL);
                        if (bios->data) {
                                memcpy_fromio(bios->data, rom, length);
                                bios->length = length;
                        }
-                       pci_unmap_rom(pdev, rom);
                }
+               if (rom)
+                       pci_unmap_rom(pdev, rom);
 
                pci_disable_rom(pdev);
        }