Commit 60063a66 authored Oct 28, 2008 by Steven Rostedt Committed by Ingo Molnar Oct 28, 2008

ftrace: fix current_tracer error return



The commit (in linux-tip) c2931e05
 ( ftrace: return an error when setting a nonexistent tracer )
added useful code that would error when a bad tracer was written into
the current_tracer file.

But this had a bug if the amount written was more than the amount read by
that code. The first iteration would set the tracer correctly, but since
it did not consume the rest of what was written (usually whitespace), the
userspace utility would continue to write what was not consumed. This
second iteration would fail to find a tracer and return -EINVAL. Funny
thing is that the tracer would have already been set.

This patch just consumes all the data that is written to the file.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 21798a84

kernel/trace/trace.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -2377,9 +2377,10 @@ tracing_set_trace_write(struct file filp, const char __user ubuf,
		int i;
		size_t ret;

		ret = cnt;

		if (cnt > max_tracer_type_len)
		cnt = max_tracer_type_len;
		ret = cnt;

		if (copy_from_user(&buf, ubuf, cnt))
		return -EFAULT;
		@@ -2412,8 +2413,8 @@ tracing_set_trace_write(struct file filp, const char __user ubuf,
		out:
		mutex_unlock(&trace_types_lock);

		if (ret == cnt)
		filp->f_pos += cnt;
		if (ret > 0)
		filp->f_pos += ret;

		return ret;
		}

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