linux-kernel - [PATCH] security: declare member holding string literal const

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Message-Id: <20220217141858.71281-1-cgzones@googlemail.com>
Date:   Thu, 17 Feb 2022 15:18:57 +0100
From:   Christian Göttsche <cgzones@...glemail.com>
To:     selinux@...r.kernel.org
Cc:     James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Paul Moore <paul@...l-moore.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Xin Long <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Mickaël Salaün <mic@...ux.microsoft.com>,
        Todd Kjos <tkjos@...gle.com>,
        Olga Kornievskaia <kolga@...app.com>,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH] security: declare member holding string literal const

The struct security_hook_list member lsm is assigned in
security_add_hooks() with string literals passed from the individual
security modules.  Declare the function parameter and the struct member
const to signal their immutability.

Reported by Clang [-Wwrite-strings]:

    security/selinux/hooks.c:7388:63: error: passing 'const char [8]' to parameter of type 'char *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
            security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks), selinux);
                                                                         ^~~~~~~~~
    ./include/linux/lsm_hooks.h:1629:11: note: passing argument to parameter 'lsm' here
                                    char *lsm);
                                          ^

Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
---
 include/linux/lsm_hooks.h | 4 ++--
 security/security.c       | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 419b5febc3ca..47cdf3fbecef 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1595,7 +1595,7 @@ struct security_hook_list {
 	struct hlist_node		list;
 	struct hlist_head		*head;
 	union security_list_options	hook;
-	char				*lsm;
+	const char			*lsm;
 } __randomize_layout;
 
 /*
@@ -1630,7 +1630,7 @@ extern struct security_hook_heads security_hook_heads;
 extern char *lsm_names;
 
 extern void security_add_hooks(struct security_hook_list *hooks, int count,
-				char *lsm);
+				const char *lsm);
 
 #define LSM_FLAG_LEGACY_MAJOR	BIT(0)
 #define LSM_FLAG_EXCLUSIVE	BIT(1)
diff --git a/security/security.c b/security/security.c
index 9663ffcca4b0..a48eb3badfdd 100644
--- a/security/security.c
+++ b/security/security.c
@@ -478,7 +478,7 @@ static int lsm_append(const char *new, char **result)
  * Each LSM has to register its hooks with the infrastructure.
  */
 void __init security_add_hooks(struct security_hook_list *hooks, int count,
-				char *lsm)
+				const char *lsm)
 {
 	int i;
 
-- 
2.35.1