selinux: free str on error in str_read()

In [see "Fixes:"] I missed the fact that str_read() may give back an
allocated pointer even if it returns an error, causing a potential
memory leak in filename_trans_read_one(). Fix this by making the
function free the allocated string whenever it returns a non-zero value,
which also makes its behavior more obvious and prevents repeating the
same mistake in the future.

Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1461665 ("Resource leaks")
Fixes: df2852430e39 ("selinux: optimize storage of filename transitions")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 70ecdc78efbd9f148d5a6744f4981ded87e5aac3..c21b922e5ebec1c851c74c22d43e17c39ff0c4e8 100644 (file)
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -1035,14 +1035,14 @@ static int str_read(char **strp, gfp_t flags, void *fp, u32 len)
        if (!str)
                return -ENOMEM;
 
-       /* it's expected the caller should free the str */
-       *strp = str;
-
        rc = next_entry(str, fp, len);
-       if (rc)
+       if (rc) {
+               kfree(str);
                return rc;
+       }
 
        str[len] = '\0';
+       *strp = str;
        return 0;
 }