linux-kernel - [PATCH] tracing/uprobe: Replace strlcpy() with strscpy()

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Message-Id: <20231130205607.work.463-kees@kernel.org>
Date:   Thu, 30 Nov 2023 12:56:08 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH] tracing/uprobe: Replace strlcpy() with strscpy()

strlcpy() reads the entire source buffer first. This read may exceed
the destination size limit. This is both inefficient and can lead
to linear read overflows if a source string is not NUL-terminated[1].
Additionally, it returns the size of the source string, not the
resulting size of the destination string. In an effort to remove strlcpy()
completely[2], replace strlcpy() here with strscpy().

The negative return value is already handled by this code so no new
handling is needed here.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1]
Link: https://github.com/KSPP/linux/issues/89 [2]
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: linux-trace-kernel@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 kernel/trace/trace_uprobe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 99c051de412a..a84b85d8aac1 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -151,7 +151,7 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
 		return -ENOMEM;
 
 	if (addr == FETCH_TOKEN_COMM)
-		ret = strlcpy(dst, current->comm, maxlen);
+		ret = strscpy(dst, current->comm, maxlen);
 	else
 		ret = strncpy_from_user(dst, src, maxlen);
 	if (ret >= 0) {
-- 
2.34.1