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    Subject[PATCH 3.12 010/175] PCI: Fix infinite loop with ROM image of size 0
    Date
    From: Michel Dänzer <michel.daenzer@amd.com>

    3.12-stable review patch. If anyone has any objections, please let me know.

    ===============

    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: Jiri Slaby <jslaby@suse.cz>
    ---
    drivers/pci/rom.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    diff --git a/drivers/pci/rom.c b/drivers/pci/rom.c
    index c5d0a08a8747..d6d499782fb4 100644
    --- 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 */
    --
    2.3.0


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