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

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'")
Cc: [e-mail] # v3.17+
Signed-off-by: Nicolai Stange <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/platform.c

···
 	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);