tracing: Use trace_seq_used() and seq_buf_used() instead of len
As the seq_buf->len will soon be +1 size when there's an overflow, we
must use trace_seq_used() or seq_buf_used() methods to get the real
length. This will prevent buffer overflow issues if just the len
of the seq_buf descriptor is used to copy memory.
Link: http://lkml.kernel.org/r/20141114121911.09ba3d38@gandalf.local.home
Reported-by: Petr Mladek <pmladek@suse.cz>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 85d3710..cfaf5a1 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -24,6 +24,24 @@
}
/**
+ * trace_seq_used - amount of actual data written to buffer
+ * @s: trace sequence descriptor
+ *
+ * Returns the amount of data written to the buffer.
+ *
+ * IMPORTANT!
+ *
+ * Use this instead of @s->seq.len if you need to pass the amount
+ * of data from the buffer to another buffer (userspace, or what not).
+ * The @s->seq.len on overflow is bigger than the buffer size and
+ * using it can cause access to undefined memory.
+ */
+static inline int trace_seq_used(struct trace_seq *s)
+{
+ return seq_buf_used(&s->seq);
+}
+
+/**
* trace_seq_buffer_ptr - return pointer to next location in buffer
* @s: trace sequence descriptor
*
@@ -35,7 +53,7 @@
static inline unsigned char *
trace_seq_buffer_ptr(struct trace_seq *s)
{
- return s->buffer + s->seq.len;
+ return s->buffer + seq_buf_used(&s->seq);
}
/**