linux-kernel - [GIT PULL] tracing: Two locking fixes

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Date:   Thu, 11 Nov 2021 09:08:59 -0500
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>,
        Jiri Olsa <jolsa@...hat.com>
Subject: [GIT PULL] tracing: Two locking fixes

Linus,

Two tracing fixes:

- Add mutex protection to ring_buffer_reset()

- Fix deadlock in modify_ftrace_direct_multi()


Please pull the latest trace-v5.16-3 tree, which can be found at:


  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
trace-v5.16-3

Tag SHA1: 04b4f472203407d85d8ca937f8f2dbe265f87d84
Head SHA1: 2e6e9058d13a22a6fdd36a8c444ac71d9656003a


Jiri Olsa (1):
      ftrace/direct: Fix lockup in modify_ftrace_direct_multi

Steven Rostedt (VMware) (1):
      ring-buffer: Protect ring_buffer_reset() from reentrancy

----
 kernel/trace/ftrace.c      | 3 ++-
 kernel/trace/ring_buffer.c | 5 +++++
 2 files changed, 7 insertions(+), 1 deletion(-)
---------------------------
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b4ed1a301232..fc49e8809a56 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5602,10 +5602,11 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
 		}
 	}
 
+	mutex_unlock(&ftrace_lock);
+
 	/* Removing the tmp_ops will add the updated direct callers to the functions */
 	unregister_ftrace_function(&tmp_ops);
 
-	mutex_unlock(&ftrace_lock);
  out_direct:
 	mutex_unlock(&direct_mutex);
 	return err;
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index f6520d0a4c8c..2699e9e562b1 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5228,6 +5228,9 @@ void ring_buffer_reset(struct trace_buffer *buffer)
 	struct ring_buffer_per_cpu *cpu_buffer;
 	int cpu;
 
+	/* prevent another thread from changing buffer sizes */
+	mutex_lock(&buffer->mutex);
+
 	for_each_buffer_cpu(buffer, cpu) {
 		cpu_buffer = buffer->buffers[cpu];
 
@@ -5246,6 +5249,8 @@ void ring_buffer_reset(struct trace_buffer *buffer)
 		atomic_dec(&cpu_buffer->record_disabled);
 		atomic_dec(&cpu_buffer->resize_disabled);
 	}
+
+	mutex_unlock(&buffer->mutex);
 }
 EXPORT_SYMBOL_GPL(ring_buffer_reset);