linux-kernel - [PATCH] tracing: replace deprecated strncpy with strscpy

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Message-ID: <20240826-strncpy-kernel-trace-trace_branch-c-v1-1-b2c14f2e9e84@google.com>
Date: Mon, 26 Aug 2024 10:40:49 -0700
From: Justin Stitt <justinstitt@...gle.com>
To: Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	Kees Cook <kees@...nel.org>, linux-hardening@...r.kernel.org, 
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] tracing: 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 [1]
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@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
 kernel/trace/trace_branch.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index e47fdb4c92fb..aa63548873c3 100644
--- 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;

---
base-commit: 521b1e7f4cf0b05a47995b103596978224b380a8
change-id: 20240820-strncpy-kernel-trace-trace_branch-c-0a953ebcdfe1

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