PCI: Don't read past the end of sysfs "driver_override" buffer

commit 4efe874aace57dba967624ce1c48322da2447b75 upstream.

When printing the driver_override parameter when it is 4095 and 4094 bytes
long, the printing code would access invalid memory because we need count+1
bytes for printing.

Fixes: 782a985d7af2 ("PCI: Introduce new device binding path using pci_dev.driver_override")
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: Alexander Graf <agraf@suse.de>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 6d04771e49036ba53e9b79ea665440ffb43d6204..045b63ae97d5501cf9fad5d66202cbc2acee0ef7 100644 (file)
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -516,7 +516,8 @@ static ssize_t driver_override_store(struct device *dev,
        struct pci_dev *pdev = to_pci_dev(dev);
        char *driver_override, *old = pdev->driver_override, *cp;
 
-       if (count > PATH_MAX)
+       /* We need to keep extra room for a newline */
+       if (count >= (PAGE_SIZE - 1))
                return -EINVAL;
 
        driver_override = kstrndup(buf, count, GFP_KERNEL);
@@ -544,7 +545,7 @@ static ssize_t driver_override_show(struct device *dev,
 {
        struct pci_dev *pdev = to_pci_dev(dev);
 
-       return sprintf(buf, "%s\n", pdev->driver_override);
+       return snprintf(buf, PAGE_SIZE, "%s\n", pdev->driver_override);
 }
 static DEVICE_ATTR_RW(driver_override);