From: Chuck Lever <chuck.lever@oracle.com>

Date: Wed, 6 Apr 2022 13:51:32 -0400

Subject: SUNRPC: Fix the svc_deferred_event trace class

Git-commit: 4d5004451ab2218eab94a30e1841462c9316ba19

Patch-mainline: v5.18-rc3

References: git-fixes

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.

Unfortunately we can't revert the "svc_deferred_class" hunk in

commit ece200ddd54b ("sunrpc: Save remote presentation address in

svc_xprt for trace events") because there is now a specific check

of event format specifiers for unsafe dereferences. The warning

that check emits is:

  event svc_defer_recv has unsafe dereference of argument 1

A "%pISpc" format specifier with a "struct sockaddr *" is indeed

flagged by this check.

Instead, take the brute-force approach used by the svcrdma_qp_error

tracepoint. Convert the dr::addr field into a presentation address

in the TP_fast_assign() arm of the trace event, and store that as

a string. This fix can be backported to -stable kernels.

In the meantime, commit c6ced22997ad ("tracing: Update print fmt

check to handle new __get_sockaddr() macro") is now in v5.18, so

this wonky fix can be replaced with __sockaddr() and friends

properly during the v5.19 merge window.

Fixes: ece200ddd54b ("sunrpc: Save remote presentation address in svc_xprt for trace events")

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Acked-by: Petr Pavlu <petr.pavlu@suse.com>

---

 include/trace/events/sunrpc.h | 7 ++++---

 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h

index ab8ae1f6ba84..4eb706fa5825 100644

--- a/include/trace/events/sunrpc.h

+++ b/include/trace/events/sunrpc.h

@@ -2017,16 +2017,17 @@ DECLARE_EVENT_CLASS(svc_deferred_event,

 	TP_STRUCT__entry(

 		__field(u32, xid)

-		__string(addr, dr->xprt->xpt_remotebuf)

+		__array(__u8, addr, INET6_ADDRSTRLEN + 10)

 	),

 	TP_fast_assign(

 		__entry->xid = be32_to_cpu(*(__be32 *)(dr->args +

 						       (dr->xprt_hlen>>2)));

-		__assign_str(addr, dr->xprt->xpt_remotebuf);

+		snprintf(__entry->addr, sizeof(__entry->addr) - 1,

+			 "%pISpc", (struct sockaddr *)&dr->addr);

 	),

-	TP_printk("addr=%s xid=0x%08x", __get_str(addr), __entry->xid)

+	TP_printk("addr=%s xid=0x%08x", __entry->addr, __entry->xid)

 );

 DEFINE_EVENT(svc_deferred_event, svc_drop_deferred,