2 files changed, 14 insertions, 4 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 4451aa3a55a0..7693aaf324c6 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2437,7 +2437,7 @@ static void reset_iter_read(struct ftrace_iterator *iter)
 {
         iter->pos = 0;
         iter->func_pos = 0;
-        iter->flags &= ~(FTRACE_ITER_PRINTALL & FTRACE_ITER_HASH);
+        iter->flags &= ~(FTRACE_ITER_PRINTALL | FTRACE_ITER_HASH);
 }
 
 static void *t_start(struct seq_file *m, loff_t *pos)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 3c7834c24e54..ce8514feedcd 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1397,6 +1397,8 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
                 struct list_head *head_page_with_bit;
 
                 head_page = &rb_set_head_page(cpu_buffer)->list;
+                if (!head_page)
+                        break;
                 prev_page = head_page->prev;
 
                 first_page = pages->next;
@@ -2937,7 +2939,7 @@ u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
         unsigned long flags;
         struct ring_buffer_per_cpu *cpu_buffer;
         struct buffer_page *bpage;
-        u64 ret;
+        u64 ret = 0;
 
         if (!cpumask_test_cpu(cpu, buffer->cpumask))
                 return 0;
@@ -2952,7 +2954,8 @@ u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
                 bpage = cpu_buffer->reader_page;
         else
                 bpage = rb_set_head_page(cpu_buffer);
-        ret = bpage->page->time_stamp;
+        if (bpage)
+                ret = bpage->page->time_stamp;
         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
         return ret;
@@ -3288,6 +3291,8 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
          * Splice the empty reader page into the list around the head.
          */
         reader = rb_set_head_page(cpu_buffer);
+        if (!reader)
+                goto out;
         cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
         cpu_buffer->reader_page->list.prev = reader->list.prev;
 
@@ -3806,12 +3811,17 @@ void
 ring_buffer_read_finish(struct ring_buffer_iter *iter)
 {
         struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+        unsigned long flags;
 
         /*
          * Ring buffer is disabled from recording, here's a good place
-         * to check the integrity of the ring buffer. 
+         * to check the integrity of the ring buffer.
+         * Must prevent readers from trying to read, as the check
+         * clears the HEAD page and readers require it.
          */
+        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(&cpu_buffer->record_disabled);
         atomic_dec(&cpu_buffer->buffer->resize_disabled);