[PATCH 3.2 015/221] PCI: Fix infinite loop with ROM image of size 0

Ben Hutchings
2015-05-05T02:36:53Z

From: Michel Dänzer <michel.daenzer@amd.com>

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: Ben Hutchings <ben@decadent.org.uk>
---
drivers/pci/rom.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/pci/rom.c
+++ b/drivers/pci/rom.c
@@ -69,6 +69,7 @@ size_t pci_get_rom_size(struct pci_dev *
{
void __iomem *image;
int last_image;
+ unsigned length;

image = rom;
do {
@@ -91,9 +92,9 @@ size_t pci_get_rom_size(struct pci_dev *
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 */