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 [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
drivers/pnp/pnpacpi/core.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/drivers/pnp/pnpacpi/core.c b/drivers/pnp/pnpacpi/core.c
index 6ab272c84b7b..a0927081a003 100644
--- 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);
---
base-commit: dab3e01664eaddae965699f1fec776609db0ea9d
change-id: 20231019-strncpy-drivers-pnp-pnpacpi-core-c-54d9bc42443e
Best regards,
--
Justin Stitt <[email protected]>
On Thu, Oct 19, 2023 at 10:47:58PM +0000, Justin Stitt wrote:
> 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 [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
Looks clean to me!
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
On Fri, Oct 20, 2023 at 1:06 AM Kees Cook <[email protected]> wrote:
>
> On Thu, Oct 19, 2023 at 10:47:58PM +0000, Justin Stitt wrote:
> > 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 [1]
> > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> > Link: https://github.com/KSPP/linux/issues/90
> > Cc: [email protected]
> > Signed-off-by: Justin Stitt <[email protected]>
>
> Looks clean to me!
>
> Reviewed-by: Kees Cook <[email protected]>
Applied as 6.7 material, thanks!