selinux: return early for possible NULL audit buffers

audit_log_start() may return NULL in below cases:

  - when audit is not initialized.
  - when audit backlog limit exceeds.

After the call to audit_log_start() is made and then possible NULL audit
buffer argument is passed to audit_log_*() functions,
audit_log_*() functions return immediately in case of a NULL audit buffer
argument.

But it is optimal to return early when audit_log_start() returns NULL,
because it is not necessary for audit_log_*() functions to be called with
NULL audit buffer argument.

So add exception handling for possible NULL audit buffers where
return value can be handled from callers.

Signed-off-by: Austin Kim <austin.kim@lge.com>
[PM: tweak subject line]
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index b0032c4..9e84e66 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3325,6 +3325,8 @@ static int selinux_inode_setxattr(struct user_namespace *mnt_userns,
                        }
                        ab = audit_log_start(audit_context(),
                                             GFP_ATOMIC, AUDIT_SELINUX_ERR);
+                       if (!ab)
+                               return rc;
                        audit_log_format(ab, "op=setxattr invalid_context=");
                        audit_log_n_untrustedstring(ab, value, audit_size);
                        audit_log_end(ab);
@@ -6552,6 +6554,8 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
                                ab = audit_log_start(audit_context(),
                                                     GFP_ATOMIC,
                                                     AUDIT_SELINUX_ERR);
+                               if (!ab)
+                                       return error;
                                audit_log_format(ab, "op=fscreate invalid_context=");
                                audit_log_n_untrustedstring(ab, value, audit_size);
                                audit_log_end(ab);

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index d84c77f..e5f1b27 100644 (file)
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -1673,6 +1673,8 @@ static int compute_sid_handle_invalid_context(
        if (context_struct_to_string(policydb, newcontext, &n, &nlen))
                goto out;
        ab = audit_log_start(audit_context(), GFP_ATOMIC, AUDIT_SELINUX_ERR);
+       if (!ab)
+               goto out;
        audit_log_format(ab,
                         "op=security_compute_sid invalid_context=");
        /* no need to record the NUL with untrusted strings */