From: Yuntao Wang <ytcoode@gmail.com>
Date: Fri, 4 Mar 2022 15:04:08 +0800
Subject: bpf: Replace strncpy() with strscpy()
Patch-mainline: v5.18-rc1
Git-commit: 03b9c7fa3f15f51bcd07f3828c2a01311e7746c4
References: jsc#PED-1377

Using strncpy() on NUL-terminated strings is considered deprecated[1].
Moreover, if the length of 'task->comm' is less than the destination buffer
size, strncpy() will NUL-pad the destination buffer, which is a needless
performance penalty.

Replacing strncpy() with strscpy() fixes all these issues.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220304070408.233658-1-ytcoode@gmail.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 kernel/bpf/helpers.c |    9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -225,13 +225,8 @@ BPF_CALL_2(bpf_get_current_comm, char *,
 	if (unlikely(!task))
 		goto err_clear;
 
-	strncpy(buf, task->comm, size);
-
-	/* Verifier guarantees that size > 0. For task->comm exceeding
-	 * size, guarantee that buf is %NUL-terminated. Unconditionally
-	 * done here to save the size test.
-	 */
-	buf[size - 1] = 0;
+	/* Verifier guarantees that size > 0 */
+	strscpy(buf, task->comm, size);
 	return 0;
 err_clear:
 	memset(buf, 0, size);