[PATCH] pci/rom: Don't scan past the end of the ROM BAR

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

We can't trust the ROM headers to be 100% correct, and accessing
past the end of the BAR can cause really bad things, such as
machine checks on some platforms.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

Found that in an old pile of patches while cleaning up my disk :-)

I was dealing with a buggy radeon that the time iirc.

Cheers,
Ben.
 
diff --git a/drivers/pci/rom.c b/drivers/pci/rom.c
index 36864a9..d07dcfc 100644
--- a/drivers/pci/rom.c
+++ b/drivers/pci/rom.c
@@ -67,10 +67,10 @@ void pci_disable_rom(struct pci_dev *pdev)
 size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom, size_t size)
 {
 	void __iomem *image;
-	int last_image;
+	int last_image = 0;
 
 	image = rom;
-	do {
+	while (!last_image && (image - rom) < (size - 24)) {
 		void __iomem *pds;
 		/* Standard PCI ROMs start out with these bytes 55 AA */
 		if (readb(image) != 0x55) {
@@ -92,7 +92,7 @@ size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom, size_t size)
 		last_image = readb(pds + 21) & 0x80;
 		/* this length is reliable */
 		image += readw(pds + 16) * 512;
-	} while (!last_image);
+	};
 
 	/* never return a size larger than the PCI resource window */
 	/* there are known ROMs that get the size wrong */
-- 
1.7.9.1