[PATCH net] xdp: xdp_mem_allocator can be NULL in trace_mem_connect().

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: netdev@vger.kernel.org, bpf@vger.kernel.org
Cc: "Alexei Starovoitov" <ast@kernel.org>,
	"Andrii Nakryiko" <andrii@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"David S. Miller" <davem@davemloft.net>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"KP Singh" <kpsingh@kernel.org>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Song Liu" <songliubraving@fb.com>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Toke Høiland-Jørgensen" <toke@redhat.com>,
	"Yonghong Song" <yhs@fb.com>
Subject: [PATCH net] xdp: xdp_mem_allocator can be NULL in trace_mem_connect().
Date: Thu, 3 Mar 2022 13:26:47 +0100	[thread overview]
Message-ID: <YiC0BwndXiwxGDNz@linutronix.de> (raw)

Since the commit mentioned below __xdp_reg_mem_model() can return a NULL
pointer. This pointer is dereferenced in trace_mem_connect() which leads
to segfault. It can be reproduced with enabled trace events during ifup.

Only assign the arguments in the trace-event macro if `xa' is set.
Otherwise set the parameters to 0.

Fixes: 4a48ef70b93b8 ("xdp: Allow registering memory model without rxq reference")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/trace/events/xdp.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index c40fc97f94171..9196dcd08e6c7 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -362,9 +362,9 @@ TRACE_EVENT(mem_connect,
 
 	TP_fast_assign(
 		__entry->xa		= xa;
-		__entry->mem_id		= xa->mem.id;
-		__entry->mem_type	= xa->mem.type;
-		__entry->allocator	= xa->allocator;
+		__entry->mem_id		= xa ? xa->mem.id : 0;
+		__entry->mem_type	= xa ? xa->mem.type : 0;
+		__entry->allocator	= xa ? xa->allocator : NULL;
 		__entry->rxq		= rxq;
 		__entry->ifindex	= rxq->dev->ifindex;
 	),
-- 
2.35.1

