[PATCH] virt: acrn: replace deprecated strncpy with strscpy

[PATCH] virt: acrn: replace deprecated strncpy with strscpy

[Justin Stitt]

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 can see that client->name should be NUL-terminated based on its usage
with a %s C-string format specifier.
|	client->thread = kthread_run(ioreq_task, client, "VM%u-%s",
|					client->vm->vmid, client->name);

NUL-padding is not required as client is already zero-allocated:
|	client = kzalloc(sizeof(*client), 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.

Note that this patch relies on the _new_ 2-argument version of strscpy()
introduced in Commit e6584c3964f2f ("string: Allow 2-argument
strscpy()").

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: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/virt/acrn/ioreq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virt/acrn/ioreq.c b/drivers/virt/acrn/ioreq.c
index 29e1ef1915fd..e94358239a4b 100644
--- a/drivers/virt/acrn/ioreq.c
+++ b/drivers/virt/acrn/ioreq.c
@@ -433,7 +433,7 @@ struct acrn_ioreq_client *acrn_ioreq_client_create(struct acrn_vm *vm,
 	client->priv = priv;
 	client->is_default = is_default;
 	if (name)
-		strncpy(client->name, name, sizeof(client->name) - 1);
+		strscpy(client->name, name);
 	rwlock_init(&client->range_lock);
 	INIT_LIST_HEAD(&client->range_list);
 	init_waitqueue_head(&client->wq);

---
base-commit: a4145ce1e7bc247fd6f2846e8699473448717b37
change-id: 20240320-strncpy-drivers-virt-acrn-ioreq-c-9913a5c6e2bf

Best regards,
--
Justin Stitt <justinstitt@google.com>

Re: [PATCH] virt: acrn: replace deprecated strncpy with strscpy

[Kees Cook]

On Wed, Mar 20, 2024 at 11:27:09PM +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 can see that client->name should be NUL-terminated based on its usage
> with a %s C-string format specifier.
> |	client->thread = kthread_run(ioreq_task, client, "VM%u-%s",
> |					client->vm->vmid, client->name);
> 
> NUL-padding is not required as client is already zero-allocated:
> |	client = kzalloc(sizeof(*client), 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.
> 
> Note that this patch relies on the _new_ 2-argument version of strscpy()
> introduced in Commit e6584c3964f2f ("string: Allow 2-argument
> strscpy()").
> 
> 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: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH] virt: acrn: replace deprecated strncpy with strscpy

[Kees Cook]

On Wed, 20 Mar 2024 23:27:09 +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 can see that client->name should be NUL-terminated based on its usage
> with a %s C-string format specifier.
> |	client->thread = kthread_run(ioreq_task, client, "VM%u-%s",
> |					client->vm->vmid, client->name);
> 
> [...]

Applied to for-next/hardening, thanks!

[1/1] virt: acrn: replace deprecated strncpy with strscpy
      https://git.kernel.org/kees/c/e8a87d0cd048

Take care,

-- 
Kees Cook