linux-hardening - [PATCH] bpf: Replace all non-returning strlcpy with strscpy

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Date:   Tue, 30 May 2023 15:56:59 +0000
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Cc:     linux-hardening@...r.kernel.org,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ilya Leoshkevich <iii@...ux.ibm.com>
Subject: [PATCH] bpf: Replace all non-returning 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].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>
---
 kernel/bpf/preload/bpf_preload_kern.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/preload/bpf_preload_kern.c b/kernel/bpf/preload/bpf_preload_kern.c
index b56f9f3314fd..0c63bc2cd895 100644
--- a/kernel/bpf/preload/bpf_preload_kern.c
+++ b/kernel/bpf/preload/bpf_preload_kern.c
@@ -23,9 +23,9 @@ static void free_links_and_skel(void)
 
 static int preload(struct bpf_preload_info *obj)
 {
-	strlcpy(obj[0].link_name, "maps.debug", sizeof(obj[0].link_name));
+	strscpy(obj[0].link_name, "maps.debug", sizeof(obj[0].link_name));
 	obj[0].link = maps_link;
-	strlcpy(obj[1].link_name, "progs.debug", sizeof(obj[1].link_name));
+	strscpy(obj[1].link_name, "progs.debug", sizeof(obj[1].link_name));
 	obj[1].link = progs_link;
 	return 0;
 }