linux-kernel - [for-next][PATCH 01/23] tracing: Have event format check not flag %p* on __get_dynamic

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Message-ID: <20220528025248.861126787@goodmis.org>
Date:   Fri, 27 May 2022 22:50:29 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org, Stephen Rothwell <sfr@...b.auug.org.au>
Subject: [for-next][PATCH 01/23] tracing: Have event format check not flag %p* on
 __get_dynamic_array()

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

The print fmt check against trace events to make sure that the format does
not use pointers that may be freed from the time of the trace to the time
the event is read, gives a false positive on %pISpc when reading data that
was saved in __get_dynamic_array() when it is perfectly fine to do so, as
the data being read is on the ring buffer.

Link: https://lore.kernel.org/all/20220407144524.2a592ed6@canb.auug.org.au/

Cc: stable@...r.kernel.org
Fixes: 5013f454a352c ("tracing: Add check of trace event print fmts for dereferencing pointers")
Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_events.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 78f313b7b315..d5913487821a 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -392,12 +392,6 @@ static void test_event_printk(struct trace_event_call *call)
 			if (!(dereference_flags & (1ULL << arg)))
 				goto next_arg;
 
-			/* Check for __get_sockaddr */;
-			if (str_has_prefix(fmt + i, "__get_sockaddr(")) {
-				dereference_flags &= ~(1ULL << arg);
-				goto next_arg;
-			}
-
 			/* Find the REC-> in the argument */
 			c = strchr(fmt + i, ',');
 			r = strstr(fmt + i, "REC->");
@@ -413,7 +407,14 @@ static void test_event_printk(struct trace_event_call *call)
 				a = strchr(fmt + i, '&');
 				if ((a && (a < r)) || test_field(r, call))
 					dereference_flags &= ~(1ULL << arg);
+			} else if ((r = strstr(fmt + i, "__get_dynamic_array(")) &&
+				   (!c || r < c)) {
+				dereference_flags &= ~(1ULL << arg);
+			} else if ((r = strstr(fmt + i, "__get_sockaddr(")) &&
+				   (!c || r < c)) {
+				dereference_flags &= ~(1ULL << arg);
 			}
+
 		next_arg:
 			i--;
 			arg++;
-- 
2.35.1