driver core: platform: Don't read past the end of "driver_override" buffer

commit bf563b01c2895a4bfd1a29cc5abc67fe706ecffd 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.

Reject driver_override values of these lengths in driver_override_store().

This is in close analogy to commit 4efe874aace5 ("PCI: Don't read past the
end of sysfs "driver_override" buffer") from Sasha Levin.

Fixes: 3d713e0e382e ("driver core: platform: add device binding path 'driver_override'")
Signed-off-by: Nicolai Stange <nstange@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 5eba478..14ff403 100644 (file)
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -858,7 +858,8 @@ static ssize_t driver_override_store(struct device *dev,
        struct platform_device *pdev = to_platform_device(dev);
        char *driver_override, *old, *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);