Merging upstream version 6.9.7.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 6511dc3a00..54887f4c35 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1449,6 +1449,11 @@ static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
  *
  * As a safety measure we check to make sure the data pages have not
  * been corrupted.
+ *
+ * Callers of this function need to guarantee that the list of pages doesn't get
+ * modified during the check. In particular, if it's possible that the function
+ * is invoked with concurrent readers which can swap in a new reader page then
+ * the caller should take cpu_buffer->reader_lock.
  */
 static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
 {
@@ -2200,8 +2205,12 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
 		 */
 		synchronize_rcu();
 		for_each_buffer_cpu(buffer, cpu) {
+			unsigned long flags;
+
 			cpu_buffer = buffer->buffers[cpu];
+			raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
 			rb_check_pages(cpu_buffer);
+			raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 		}
 		atomic_dec(&buffer->record_disabled);
 	}