tracing: limit the number of loops the ring buffer self test can make

Impact: prevent deadlock if ring buffer gets corrupted

This patch adds a paranoid check to make sure the ring buffer consumer
does not go into an infinite loop. Since the ring buffer has been set
to read only, the consumer should not loop for more than the ring buffer
size. A check is added to make sure the consumer does not loop more than
the ring buffer size.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index a7e0ef662f9f9bd593949b6d66f1e3872baf04b3..bc8e80a86bca4c0cf730fcf6b7bc568f2808f7e7 100644 (file)
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -23,10 +23,20 @@ static int trace_test_buffer_cpu(struct trace_array *tr, int cpu)
 {
        struct ring_buffer_event *event;
        struct trace_entry *entry;
+       unsigned int loops = 0;
 
        while ((event = ring_buffer_consume(tr->buffer, cpu, NULL))) {
                entry = ring_buffer_event_data(event);
 
+               /*
+                * The ring buffer is a size of trace_buf_size, if
+                * we loop more than the size, there's something wrong
+                * with the ring buffer.
+                */
+               if (loops++ > trace_buf_size) {
+                       printk(KERN_CONT ".. bad ring buffer ");
+                       goto failed;
+               }
                if (!trace_valid_entry(entry)) {
                        printk(KERN_CONT ".. invalid entry %d ",
                                entry->type);