[PATCH] tracing/probes: Add const to new_argv allocation type

[PATCH] tracing/probes: Add const to new_argv allocation type

[Kees Cook]

From: Kees Cook <kees+treewide@kernel.org>

In preparation for converting the kmalloc family of allocators to the
type-aware kmalloc_obj family, we need to make sure that the returned
type from the allocation matches the type of the variable being
assigned. (The kmalloc family returns "void *", which can be implicitly
cast to any pointer type.)

The assigned type is "const char **", but the converted allocation type
would be "char **", which is the same type without the const qualifier.
As there is no general way to safely add const qualifiers, take the size
from the assignment target instead. No change in allocation size
results.

Build tested ARCH=x86_64 allmodconfig with GCC 16.2.0:
kernel/trace/trace_probe.o

Assisted-by: LLM coccinelle
Signed-off-by: Kees Cook <kees+treewide@kernel.org>
---
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: <linux-trace-kernel@vger.kernel.org>
---
 kernel/trace/trace_probe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 804442b2f7d2..cfb710095f65 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -2316,7 +2316,7 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
 	else
 		*new_argc = argc;
 
-	new_argv = kcalloc(*new_argc, sizeof(char *), GFP_KERNEL);
+	new_argv = kcalloc(*new_argc, sizeof(*new_argv), GFP_KERNEL);
 	if (!new_argv)
 		return ERR_PTR(-ENOMEM);
 
-- 
2.34.1

Re: [PATCH] tracing/probes: Add const to new_argv allocation type

[Masami Hiramatsu]

On Thu, 17 Sep 2026 14:10:23 -0700
Kees Cook <kees@kernel.org> wrote:

> From: Kees Cook <kees+treewide@kernel.org>
> 
> In preparation for converting the kmalloc family of allocators to the
> type-aware kmalloc_obj family, we need to make sure that the returned
> type from the allocation matches the type of the variable being
> assigned. (The kmalloc family returns "void *", which can be implicitly
> cast to any pointer type.)
> 
> The assigned type is "const char **", but the converted allocation type
> would be "char **", which is the same type without the const qualifier.
> As there is no general way to safely add const qualifiers, take the size
> from the assignment target instead. No change in allocation size
> results.

This looks good to me. Let me pick it for-next.

Thanks!

> 
> Build tested ARCH=x86_64 allmodconfig with GCC 16.2.0:
> kernel/trace/trace_probe.o
> 
> Assisted-by: LLM coccinelle
> Signed-off-by: Kees Cook <kees+treewide@kernel.org>
> ---
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: <linux-trace-kernel@vger.kernel.org>
> ---
>  kernel/trace/trace_probe.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 804442b2f7d2..cfb710095f65 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -2316,7 +2316,7 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[],
>  	else
>  		*new_argc = argc;
>  
> -	new_argv = kcalloc(*new_argc, sizeof(char *), GFP_KERNEL);
> +	new_argv = kcalloc(*new_argc, sizeof(*new_argv), GFP_KERNEL);
>  	if (!new_argv)
>  		return ERR_PTR(-ENOMEM);
>  
> -- 
> 2.34.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>