[PATCH 5.15 169/201] tracing: Have event format check not flag %p* on __get_dynamic_array()

Greg Kroah-Hartman
2022-07-27T17:22:05Z

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

[ Upstream commit 499f12168aebd6da8fa32c9b7d6203ca9b5eb88d ]

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@vger.kernel.org
Fixes: 5013f454a352c ("tracing: Add check of trace event print fmts for dereferencing pointers")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/trace/trace_events.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index c072e8b9849c..ea3fbfa87fdd 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -407,7 +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