[PATCH RESEND] apparmor: Replace sprintf/strcpy with scnprintf/strscpy in aa_policy_init

[Thorsten Blum]

strcpy() is deprecated and sprintf() does not perform bounds checking
either. Although an overflow is unlikely, it's better to proactively
avoid it by using the safer strscpy() and scnprintf(), respectively.

Additionally, unify memory allocation for 'hname' to simplify and
improve aa_policy_init().

Link: https://github.com/KSPP/linux/issues/88
Reviewed-by: Serge Hallyn <serge at hallyn.com>
Signed-off-by: Thorsten Blum <thorsten.blum at linux.dev>
---
 security/apparmor/lib.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/security/apparmor/lib.c b/security/apparmor/lib.c
index 82dbb97ad406..acf7f5189bec 100644
--- a/security/apparmor/lib.c
+++ b/security/apparmor/lib.c
@@ -478,19 +478,17 @@ bool aa_policy_init(struct aa_policy *policy, const char *prefix,
 		    const char *name, gfp_t gfp)
 {
 	char *hname;
+	size_t hname_sz;
 
+	hname_sz = (prefix ? strlen(prefix) + 2 : 0) + strlen(name) + 1;
 	/* freed by policy_free */
-	if (prefix) {
-		hname = aa_str_alloc(strlen(prefix) + strlen(name) + 3, gfp);
-		if (hname)
-			sprintf(hname, "%s//%s", prefix, name);
-	} else {
-		hname = aa_str_alloc(strlen(name) + 1, gfp);
-		if (hname)
-			strcpy(hname, name);
-	}
+	hname = aa_str_alloc(hname_sz, gfp);
 	if (!hname)
 		return false;
+	if (prefix)
+		scnprintf(hname, hname_sz, "%s//%s", prefix, name);
+	else
+		strscpy(hname, name, hname_sz);
 	policy->hname = hname;
 	/* base.name is a substring of fqname */
 	policy->name = basename(policy->hname);
-- 
2.51.1