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From:   Romain Perier <romain.perier@gmail.com>
To:     Kees Cook <keescook@chromium.org>,
        kernel-hardening@lists.openwall.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Romain Perier <romain.perier@gmail.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        linux-kernel@vger.kernel.org
Subject: [PATCH 05/20] kobject: Manual replacement of the deprecated strlcpy() with return values
Date:   Mon, 22 Feb 2021 16:12:16 +0100
Message-Id: <20210222151231.22572-6-romain.perier@gmail.com>
In-Reply-To: <20210222151231.22572-1-romain.perier@gmail.com>
References: <20210222151231.22572-1-romain.perier@gmail.com>
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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@gmail.com>
---
 lib/kobject_uevent.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 7998affa45d4..9dca89b76a22 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -251,11 +251,11 @@ static int kobj_usermode_filter(struct kobject *kobj)
 
 static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
 {
-	int len;
+	ssize_t len;
 
-	len = strlcpy(&env->buf[env->buflen], subsystem,
+	len = strscpy(&env->buf[env->buflen], subsystem,
 		      sizeof(env->buf) - env->buflen);
-	if (len >= (sizeof(env->buf) - env->buflen)) {
+	if (len == -E2BIG) {
 		WARN(1, KERN_ERR "init_uevent_argv: buffer size too small\n");
 		return -ENOMEM;
 	}