linux-kernel - [GIT PULL] tracing: A couple of fixes

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Message-ID: <20200930195359.01d9f770@oasis.local.home>
Date:   Wed, 30 Sep 2020 19:53:59 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] tracing: A couple of fixes


Linus,

Two tracing fixes:

- Fix temp buffer accounting that caused a WARNING for
  ftrace_dump_on_opps()

- Move the recursion check in one of the function callback helpers to the
  beginning of the function, as if the rcu_is_watching() gets traced, it
  will cause a recursive loop that will crash the kernel.


Please pull the latest trace-v5.9-rc6 tree, which can be found at:


  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
trace-v5.9-rc6

Tag SHA1: 87d55eca1585b1bd70fe7de33cd5ea2957628027
Head SHA1: b40341fad6cc2daa195f8090fd3348f18fff640a


Steven Rostedt (VMware) (2):
      tracing: Fix trace_find_next_entry() accounting of temp buffer size
      ftrace: Move RCU is watching check after recursion check

----
 kernel/trace/ftrace.c |  6 ++----
 kernel/trace/trace.c  | 10 ++++++----
 2 files changed, 8 insertions(+), 8 deletions(-)
---------------------------
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 603255f5f085..541453927c82 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6993,16 +6993,14 @@ static void ftrace_ops_assist_func(unsigned long ip, unsigned long parent_ip,
 {
 	int bit;
 
-	if ((op->flags & FTRACE_OPS_FL_RCU) && !rcu_is_watching())
-		return;
-
 	bit = trace_test_and_set_recursion(TRACE_LIST_START, TRACE_LIST_MAX);
 	if (bit < 0)
 		return;
 
 	preempt_disable_notrace();
 
-	op->func(ip, parent_ip, op, regs);
+	if (!(op->flags & FTRACE_OPS_FL_RCU) || rcu_is_watching())
+		op->func(ip, parent_ip, op, regs);
 
 	preempt_enable_notrace();
 	trace_clear_recursion(bit);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2a7c26345e83..d3e5de717df2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3546,13 +3546,15 @@ struct trace_entry *trace_find_next_entry(struct trace_iterator *iter,
 	if (iter->ent && iter->ent != iter->temp) {
 		if ((!iter->temp || iter->temp_size < iter->ent_size) &&
 		    !WARN_ON_ONCE(iter->temp == static_temp_buf)) {
-			kfree(iter->temp);
-			iter->temp = kmalloc(iter->ent_size, GFP_KERNEL);
-			if (!iter->temp)
+			void *temp;
+			temp = kmalloc(iter->ent_size, GFP_KERNEL);
+			if (!temp)
 				return NULL;
+			kfree(iter->temp);
+			iter->temp = temp;
+			iter->temp_size = iter->ent_size;
 		}
 		memcpy(iter->temp, iter->ent, iter->ent_size);
-		iter->temp_size = iter->ent_size;
 		iter->ent = iter->temp;
 	}
 	entry = __find_next_entry(iter, ent_cpu, NULL, ent_ts);