tracing/branch-profiler: 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.

Both of these fields want to be NUL-terminated as per their use in
printk:

    F_printk("%u:%s:%s (%u)%s",
      __entry->line,
      __entry->func, __entry->file, __entry->correct,
      __entry->constant ? " CONSTANT" : "")

Use strscpy() as it NUL-terminates the destination buffer, so it doesn't
have to be done manually.

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
Cc: linux-hardening@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/20240826-strncpy-kernel-trace-trace_branch-c-v1-1-b2c14f2e9e84@google.com
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index e47fdb4c92fbcb8b4e0813b55371d90c3c3d2dd9..aa63548873c36f4b852ad00d0c4ccb5af8fd065a 100644 (file)
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -74,10 +74,8 @@ probe_likely_condition(struct ftrace_likely_data *f, int val, int expect)
                p--;
        p++;
 
-       strncpy(entry->func, f->data.func, TRACE_FUNC_SIZE);
-       strncpy(entry->file, p, TRACE_FILE_SIZE);
-       entry->func[TRACE_FUNC_SIZE] = 0;
-       entry->file[TRACE_FILE_SIZE] = 0;
+       strscpy(entry->func, f->data.func);
+       strscpy(entry->file, p);
        entry->constant = f->constant;
        entry->line = f->data.line;
        entry->correct = val == expect;