PNP: ACPI: replace deprecated strncpy() with strscpy()

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We know dev->name should be NUL-terminated based on the presence of a
manual NUL-byte assignment.

NUL-padding is not required as dev is already zero-allocated which
renders any further NUL-byte assignments redundant:
dev = pnp_alloc_dev(&pnpacpi_protocol, num, pnpid); --->
  dev = kzalloc(sizeof(struct pnp_dev), GFP_KERNEL);

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding. This simplifies the code and makes
the intent/behavior more obvious.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/pnp/pnpacpi/core.c b/drivers/pnp/pnpacpi/core.c
index 6ab272c84b7bb4613147061791b2cf4dbcc11eda..a0927081a003fdd8bc2af42549ecacda4314f4e4 100644 (file)
--- a/drivers/pnp/pnpacpi/core.c
+++ b/drivers/pnp/pnpacpi/core.c
@@ -250,12 +250,9 @@ static int __init pnpacpi_add_device(struct acpi_device *device)
                dev->capabilities |= PNP_DISABLE;
 
        if (strlen(acpi_device_name(device)))
-               strncpy(dev->name, acpi_device_name(device), sizeof(dev->name));
+               strscpy(dev->name, acpi_device_name(device), sizeof(dev->name));
        else
-               strncpy(dev->name, acpi_device_bid(device), sizeof(dev->name));
-
-       /* Handle possible string truncation */
-       dev->name[sizeof(dev->name) - 1] = '\0';
+               strscpy(dev->name, acpi_device_bid(device), sizeof(dev->name));
 
        if (dev->active)
                pnpacpi_parse_allocated_resource(dev);