linux-kernel - [RFC PATCH v2 09/22] selinux: make use of str

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Message-ID: <20241216164055.96267-9-cgoettsche@seltendoof.de>
Date: Mon, 16 Dec 2024 17:40:07 +0100
From: Christian Göttsche <cgoettsche@...tendoof.de>
To: selinux@...r.kernel.org
Cc: Christian Göttsche <cgzones@...glemail.com>,
	Paul Moore <paul@...l-moore.com>,
	Stephen Smalley <stephen.smalley.work@...il.com>,
	Ondrej Mosnacek <omosnace@...hat.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Thiébaud Weksteen <tweek@...gle.com>,
	Bram Bonné <brambonne@...gle.com>,
	Masahiro Yamada <masahiroy@...nel.org>,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
Subject: [RFC PATCH v2 09/22] selinux: make use of str_read()

From: Christian Göttsche <cgzones@...glemail.com>

Simplify the call sites, and enable future string validation in a single
place.

Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
---
 security/selinux/ss/conditional.c | 10 ++--------
 security/selinux/ss/policydb.c    | 22 ++++++++--------------
 security/selinux/ss/policydb.h    |  2 ++
 3 files changed, 12 insertions(+), 22 deletions(-)

diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
index d8dcaf2ca88f..1bebfcb9c6a1 100644
--- a/security/selinux/ss/conditional.c
+++ b/security/selinux/ss/conditional.c
@@ -230,17 +230,11 @@ int cond_read_bool(struct policydb *p, struct symtab *s, struct policy_file *fp)
 		goto err;
 
 	len = le32_to_cpu(buf[2]);
-	if (((len == 0) || (len == (u32)-1)))
-		goto err;
 
-	rc = -ENOMEM;
-	key = kmalloc(len + 1, GFP_KERNEL);
-	if (!key)
-		goto err;
-	rc = next_entry(key, fp, len);
+	rc = str_read(&key, GFP_KERNEL, fp, len);
 	if (rc)
 		goto err;
-	key[len] = '\0';
+
 	rc = symtab_insert(s, key, booldatum);
 	if (rc)
 		goto err;
diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index f7d0867428f5..2408c3e8ae39 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -1095,7 +1095,7 @@ static int context_read_and_validate(struct context *c, struct policydb *p,
  * binary representation file.
  */
 
-static int str_read(char **strp, gfp_t flags, struct policy_file *fp, u32 len)
+int str_read(char **strp, gfp_t flags, struct policy_file *fp, u32 len)
 {
 	int rc;
 	char *str;
@@ -2475,24 +2475,18 @@ int policydb_read(struct policydb *p, struct policy_file *fp)
 		goto bad;
 	}
 
-	rc = -ENOMEM;
-	policydb_str = kmalloc(len + 1, GFP_KERNEL);
-	if (!policydb_str) {
-		pr_err("SELinux:  unable to allocate memory for policydb "
-		       "string of length %d\n",
-		       len);
-		goto bad;
-	}
-
-	rc = next_entry(policydb_str, fp, len);
+	rc = str_read(&policydb_str, GFP_KERNEL, fp, len);
 	if (rc) {
-		pr_err("SELinux:  truncated policydb string identifier\n");
-		kfree(policydb_str);
+		if (rc == -ENOMEM) {
+			pr_err("SELinux:  unable to allocate memory for policydb string of length %d\n",
+			       len);
+		} else {
+			pr_err("SELinux:  truncated policydb string identifier\n");
+		}
 		goto bad;
 	}
 
 	rc = -EINVAL;
-	policydb_str[len] = '\0';
 	if (strcmp(policydb_str, POLICYDB_STRING)) {
 		pr_err("SELinux:  policydb string %s does not match "
 		       "my string %s\n",
diff --git a/security/selinux/ss/policydb.h b/security/selinux/ss/policydb.h
index 80d1fa7e4995..25650224b6e7 100644
--- a/security/selinux/ss/policydb.h
+++ b/security/selinux/ss/policydb.h
@@ -386,6 +386,8 @@ static inline char *sym_name(struct policydb *p, unsigned int sym_num,
 	return p->sym_val_to_name[sym_num][element_nr];
 }
 
+extern int str_read(char **strp, gfp_t flags, struct policy_file *fp, u32 len);
+
 extern u16 string_to_security_class(struct policydb *p, const char *name);
 extern u32 string_to_av_perm(struct policydb *p, u16 tclass, const char *name);
 
-- 
2.45.2