[PATCH v2] usbip: usbip_host: Replace strlcpy with strscpy

From: Azeem Shaikh <azeemshaikh38@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Valentina Manea <valentina.manea.m@gmail.com>,
	Shuah Khan <shuah@kernel.org>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Kees Cook <keescook@chromium.org>
Cc: linux-hardening@vger.kernel.org,
	Azeem Shaikh <azeemshaikh38@gmail.com>,
	Hongren Zheng <i@zenithal.me>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2] usbip: usbip_host: Replace strlcpy with strscpy
Date: Wed, 14 Jun 2023 14:10:26 +0000	[thread overview]
Message-ID: <20230614141026.2113749-1-azeemshaikh38@gmail.com> (raw)

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().

Direct replacement is safe here since return value of -errno
is used to check for truncation instead of sizeof(dest).

[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@gmail.com>
---
v1: https://lore.kernel.org/all/20230613004402.3540432-1-azeemshaikh38@gmail.com/

Changes from v1 - uses "< 0" instead of "== -E2BIG".

 drivers/usb/usbip/stub_main.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/usbip/stub_main.c b/drivers/usb/usbip/stub_main.c
index e8c3131a8543..97043b4df275 100644
--- a/drivers/usb/usbip/stub_main.c
+++ b/drivers/usb/usbip/stub_main.c
@@ -174,8 +174,7 @@ static ssize_t match_busid_store(struct device_driver *dev, const char *buf,
 		return -EINVAL;
 
 	/* busid needs to include \0 termination */
-	len = strlcpy(busid, buf + 4, BUSID_SIZE);
-	if (sizeof(busid) <= len)
+	if (strscpy(busid, buf + 4, BUSID_SIZE) < 0)
 		return -EINVAL;
 
 	if (!strncmp(buf, "add ", 4)) {
-- 
2.41.0.162.gfafddb0af9-goog


