linux-kernel - [PATCH] audit: return on memory error to avoid null pointer dereference

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Message-Id: <2000f6951431b4f19947d7aa41bb8efd2fe3f15b.1519196084.git.rgb@redhat.com>
Date:   Wed, 21 Feb 2018 04:30:07 -0500
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Paul Moore <paul@...l-moore.com>, Eric Paris <eparis@...hat.com>,
        Steve Grubb <sgrubb@...hat.com>,
        Richard Guy Briggs <rgb@...hat.com>
Subject: [PATCH] audit: return on memory error to avoid null pointer dereference

If there is a memory allocation error when trying to change an audit
kernel feature value, the ignored allocation error will trigger a NULL
pointer dereference oops on subsequent use of that pointer.  Return
instead.

Passes audit-testsuite.
See: https://github.com/linux-audit/audit-kernel/issues/76
Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
---
 kernel/audit.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/audit.c b/kernel/audit.c
index 5c25449..2de74be 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1059,6 +1059,8 @@ static void audit_log_feature_change(int which, u32 old_feature, u32 new_feature
 		return;
 
 	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_FEATURE_CHANGE);
+	if (!ab)
+		return;
 	audit_log_task_info(ab, current);
 	audit_log_format(ab, " feature=%s old=%u new=%u old_lock=%u new_lock=%u res=%d",
 			 audit_feature_names[which], !!old_feature, !!new_feature,
-- 
1.8.3.1