PCI: Fix infinite loop with ROM image of size 0

commit 16b036af31e1456cb69243a5a0c9ef801ecd1f17 upstream.

If the image size would ever read as 0, pci_get_rom_size() could keep
processing the same image over and over again.  Exit the loop if we ever
read a length of zero.

This fixes a soft lockup on boot when the radeon driver calls
pci_get_rom_size() on an AMD Radeon R7 250X PCIe discrete graphics card.

[bhelgaas: changelog, reference]
Link: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1386973
Reported-by: Federico <federicotg@gmail.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/pci/rom.c b/drivers/pci/rom.c
index c5d0a08a87473a24dc43dacb8081abf7c737b852..d6d499782fb43ad7083a7ce7f9627b75b2065407 100644 (file)
--- a/drivers/pci/rom.c
+++ b/drivers/pci/rom.c
@@ -69,6 +69,7 @@ size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom, size_t size)
 {
        void __iomem *image;
        int last_image;
+       unsigned length;
 
        image = rom;
        do {
@@ -91,9 +92,9 @@ size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom, size_t size)
                if (readb(pds + 3) != 'R')
                        break;
                last_image = readb(pds + 21) & 0x80;
-               /* this length is reliable */
-               image += readw(pds + 16) * 512;
-       } while (!last_image);
+               length = readw(pds + 16);
+               image += length * 512;
+       } while (length && !last_image);
 
        /* never return a size larger than the PCI resource window */
        /* there are known ROMs that get the size wrong */