linux-kernel - [PATCH 19/20] usbip: usbip_host: Manual replacement of the deprecated strlcpy() with return values

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Date:   Mon, 22 Feb 2021 16:12:30 +0100
From:   Romain Perier <romain.perier@...il.com>
To:     Kees Cook <keescook@...omium.org>,
        kernel-hardening@...ts.openwall.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Valentina Manea <valentina.manea.m@...il.com>,
        Shuah Khan <shuah@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Cc:     Romain Perier <romain.perier@...il.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 19/20] usbip: usbip_host: Manual replacement of the deprecated strlcpy() with return values

The strlcpy() reads the entire source buffer first, it is dangerous if
the source buffer lenght is unbounded or possibility non NULL-terminated.
It can lead to linear read overflows, crashes, etc...

As recommended in the deprecated interfaces [1], it should be replaced
by strscpy.

This commit replaces all calls to strlcpy that handle the return values
by the corresponding strscpy calls with new handling of the return
values (as it is quite different between the two functions).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy

Signed-off-by: Romain Perier <romain.perier@...il.com>
---
 drivers/usb/usbip/stub_main.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/usbip/stub_main.c b/drivers/usb/usbip/stub_main.c
index 77a5b3f8736a..5bc2c09c0d10 100644
--- a/drivers/usb/usbip/stub_main.c
+++ b/drivers/usb/usbip/stub_main.c
@@ -167,15 +167,15 @@ static ssize_t match_busid_show(struct device_driver *drv, char *buf)
 static ssize_t match_busid_store(struct device_driver *dev, const char *buf,
 				 size_t count)
 {
-	int len;
+	ssize_t len;
 	char busid[BUSID_SIZE];
 
 	if (count < 5)
 		return -EINVAL;
 
 	/* busid needs to include \0 termination */
-	len = strlcpy(busid, buf + 4, BUSID_SIZE);
-	if (sizeof(busid) <= len)
+	len = strscpy(busid, buf + 4, BUSID_SIZE);
+	if (len == -E2BIG)
 		return -EINVAL;
 
 	if (!strncmp(buf, "add ", 4)) {