[PATCH v3] integrity: check the return value of audit_log_start()

[xkernel . wang]

From: Xiaoke Wang <xkernel.wang@xxxxxxxxxxx>

audit_log_start() returns audit_buffer pointer on success or NULL on
error, so it is better to check the return value of it.

Signed-off-by: Xiaoke Wang <xkernel.wang@xxxxxxxxxxx>
Reviewed-by: Paul Moore <paul@xxxxxxxxxxxxxx>
---
Changelogs:
V2 -> V3: add the Reviewed-by tag.
V1 -> V2: simplify the patch. 
 security/integrity/integrity_audit.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/security/integrity/integrity_audit.c b/security/integrity/integrity_audit.c
index 2922005..0ec5e4c 100644
--- a/security/integrity/integrity_audit.c
+++ b/security/integrity/integrity_audit.c
@@ -45,6 +45,8 @@ void integrity_audit_message(int audit_msgno, struct inode *inode,
 		return;
 
 	ab = audit_log_start(audit_context(), GFP_KERNEL, audit_msgno);
+	if (!ab)
+		return;
 	audit_log_format(ab, "pid=%d uid=%u auid=%u ses=%u",
 			 task_pid_nr(current),
 			 from_kuid(&init_user_ns, current_uid()),
--