linux-kernel - [PATCH 06/20] ima: Manual replacement of the deprecated strlcpy() with return values

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Message-Id: <20210222151231.22572-7-romain.perier@gmail.com>
Date:   Mon, 22 Feb 2021 16:12:17 +0100
From:   Romain Perier <romain.perier@...il.com>
To:     Kees Cook <keescook@...omium.org>,
        kernel-hardening@...ts.openwall.com,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>
Cc:     Romain Perier <romain.perier@...il.com>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 06/20] ima: 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>
---
 security/integrity/ima/ima_policy.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 9b45d064a87d..1a905b8b064f 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -790,8 +790,14 @@ static int __init ima_init_arch_policy(void)
 	for (rules = arch_rules, i = 0; *rules != NULL; rules++) {
 		char rule[255];
 		int result;
+		ssize_t len;
 
-		result = strlcpy(rule, *rules, sizeof(rule));
+		len = strscpy(rule, *rules, sizeof(rule));
+		if (len == -E2BIG) {
+			pr_warn("Internal copy of architecture policy rule '%s' "
+				"failed. Skipping.\n", *rules);
+			continue;
+		}
 
 		INIT_LIST_HEAD(&arch_policy_entry[i].list);
 		result = ima_parse_rule(rule, &arch_policy_entry[i]);