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From: Justin Stitt <justinstitt@google.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
	Jason Wang <jasowang@redhat.com>,
	 Richard Weinberger <richard@nod.at>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	 Johannes Berg <johannes@sipsolutions.net>
Cc: linux-um@lists.infradead.org, linux-kernel@vger.kernel.org,
	 linux-hardening@vger.kernel.org,
	Kees Cook <keescook@chromium.org>,
	 Justin Stitt <justinstitt@google.com>
Subject: [PATCH] um,ethertap: refactor deprecated strncpy
Date: Mon, 11 Sep 2023 17:52:44 +0000	[thread overview]
Message-ID: <20230911-strncpy-arch-um-os-linux-drivers-ethertap_user-c-v1-1-d9e53f52ab32@google.com> (raw)

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

`gate_buf` should always be NUL-terminated and does not require
NUL-padding. It is used as a string arg inside an argv array given to
`run_helper()`. Due to this, let's use `strscpy` as it guarantees
NUL-terminated on the destination buffer preventing potential buffer
overreads [2].

This exact invocation was changed from `strcpy` to `strncpy` in commit
7879b1d94badb ("um,ethertap: use strncpy") back in 2015. Let's continue
hardening our `str*cpy` apis and use the newer and safer `strscpy`!

Link: 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 [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
 arch/um/os-Linux/drivers/ethertap_user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/um/os-Linux/drivers/ethertap_user.c b/arch/um/os-Linux/drivers/ethertap_user.c
index 9483021d86dd..3363851a4ae8 100644
--- a/arch/um/os-Linux/drivers/ethertap_user.c
+++ b/arch/um/os-Linux/drivers/ethertap_user.c
@@ -105,7 +105,7 @@ static int etap_tramp(char *dev, char *gate, int control_me,
 	sprintf(data_fd_buf, "%d", data_remote);
 	sprintf(version_buf, "%d", UML_NET_VERSION);
 	if (gate != NULL) {
-		strncpy(gate_buf, gate, 15);
+		strscpy(gate_buf, gate, sizeof(gate_buf));
 		args = setup_args;
 	}
 	else args = nosetup_args;

---
base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
change-id: 20230911-strncpy-arch-um-os-linux-drivers-ethertap_user-c-859160d13f59

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


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WARNING: multiple messages have this Message-ID (diff)
From: Justin Stitt <justinstitt@google.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
	Jason Wang <jasowang@redhat.com>,
	Richard Weinberger <richard@nod.at>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	Johannes Berg <johannes@sipsolutions.net>
Cc: linux-um@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-hardening@vger.kernel.org,
	Kees Cook <keescook@chromium.org>,
	Justin Stitt <justinstitt@google.com>
Subject: [PATCH] um,ethertap: refactor deprecated strncpy
Date: Mon, 11 Sep 2023 17:52:44 +0000	[thread overview]
Message-ID: <20230911-strncpy-arch-um-os-linux-drivers-ethertap_user-c-v1-1-d9e53f52ab32@google.com> (raw)

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

`gate_buf` should always be NUL-terminated and does not require
NUL-padding. It is used as a string arg inside an argv array given to
`run_helper()`. Due to this, let's use `strscpy` as it guarantees
NUL-terminated on the destination buffer preventing potential buffer
overreads [2].

This exact invocation was changed from `strcpy` to `strncpy` in commit
7879b1d94badb ("um,ethertap: use strncpy") back in 2015. Let's continue
hardening our `str*cpy` apis and use the newer and safer `strscpy`!

Link: 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 [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
 arch/um/os-Linux/drivers/ethertap_user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/um/os-Linux/drivers/ethertap_user.c b/arch/um/os-Linux/drivers/ethertap_user.c
index 9483021d86dd..3363851a4ae8 100644
--- a/arch/um/os-Linux/drivers/ethertap_user.c
+++ b/arch/um/os-Linux/drivers/ethertap_user.c
@@ -105,7 +105,7 @@ static int etap_tramp(char *dev, char *gate, int control_me,
 	sprintf(data_fd_buf, "%d", data_remote);
 	sprintf(version_buf, "%d", UML_NET_VERSION);
 	if (gate != NULL) {
-		strncpy(gate_buf, gate, 15);
+		strscpy(gate_buf, gate, sizeof(gate_buf));
 		args = setup_args;
 	}
 	else args = nosetup_args;

---
base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
change-id: 20230911-strncpy-arch-um-os-linux-drivers-ethertap_user-c-859160d13f59

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


             reply	other threads:[~2023-09-11 17:53 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-11 17:52 Justin Stitt [this message]
2023-09-11 17:52 ` [PATCH] um,ethertap: refactor deprecated strncpy Justin Stitt
2023-09-12  7:36 ` Geert Uytterhoeven
2023-09-12  7:36   ` Geert Uytterhoeven
2023-09-12 20:12   ` Justin Stitt
2023-09-12 20:12     ` Justin Stitt
2023-09-15  3:04     ` Kees Cook
2023-09-29 18:32 ` Kees Cook

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