Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Subject: [PATCH v2 2/2] SUNRPC: Fix the svc_deferred_event trace class
From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-nfs@vger.kernel.org
Date:   Wed, 06 Apr 2022 14:08:08 -0400
Message-ID: <164926848846.12216.6872977249610829189.stgit@klimt.1015granger.net>
In-Reply-To: <164926821551.12216.9112595778893638551.stgit@klimt.1015granger.net>
References: <164926821551.12216.9112595778893638551.stgit@klimt.1015granger.net>
User-Agent: StGit/1.5.dev1+g8516920
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Precedence: bulk

Fix a NULL deref crash that occurs when an svc_rqst is deferred
while the sunrpc tracing subsystem is enabled. svc_revisit() sets
dr->xprt to NULL, so it can't be relied upon in the tracepoint to
provide the remote's address.

Since __sockaddr() and friends are not available before v5.18, this
is just a partial revert of commit ece200ddd54b ("sunrpc: Save
remote presentation address in svc_xprt for trace events") in order
to enable backports of the fix. It can be cleaned up during a
future merge window.

Fixes: ece200ddd54b ("sunrpc: Save remote presentation address in svc_xprt for trace events")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/trace/events/sunrpc.h |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index ab8ae1f6ba84..4abc2fddd3b8 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -2017,18 +2017,19 @@ DECLARE_EVENT_CLASS(svc_deferred_event,
 	TP_STRUCT__entry(
 		__field(const void *, dr)
 		__field(u32, xid)
-		__string(addr, dr->xprt->xpt_remotebuf)
+		__dynamic_array(u8, addr, dr->addrlen)
 	),
 
 	TP_fast_assign(
 		__entry->dr = dr;
 		__entry->xid = be32_to_cpu(*(__be32 *)(dr->args +
 						       (dr->xprt_hlen>>2)));
-		__assign_str(addr, dr->xprt->xpt_remotebuf);
+		memcpy(__get_dynamic_array(addr), &dr->addr, dr->addrlen);
 	),
 
-	TP_printk("addr=%s dr=%p xid=0x%08x", __get_str(addr), __entry->dr,
-		__entry->xid)
+	TP_printk("addr=%pISpc dr=%p xid=0x%08x",
+		(struct sockaddr *)__get_dynamic_array(addr),
+		__entry->dr, __entry->xid)
 );
 
 #define DEFINE_SVC_DEFERRED_EVENT(name) \