Commit 5ac48378 authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
Browse files

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: default avatarPetr Mladek <pmladek@suse.cz>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 74f06bb7

include/linux/trace_seq.h

+19 −1
Original line number Diff line number Diff line
@@ -23,6 +23,24 @@ trace_seq_init(struct trace_seq *s) 
	s->full = 0;

}



/**

 * 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 @@ trace_seq_init(struct trace_seq *s) 
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);

}



/**

kernel/trace/seq_buf.c

+1 −1
Original line number Diff line number Diff line
@@ -328,7 +328,7 @@ int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt) 
	if (s->len <= s->readpos)

		return -EBUSY;



	len = s->len - s->readpos;

	len = seq_buf_used(s) - s->readpos;

	if (cnt > len)

		cnt = len;

	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);

kernel/trace/trace.c

+11 −10
Original line number Diff line number Diff line
@@ -944,10 +944,10 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt) 
{

	int len;



	if (s->seq.len <= s->seq.readpos)

	if (trace_seq_used(s) <= s->seq.readpos)

		return -EBUSY;



	len = s->seq.len - s->seq.readpos;

	len = trace_seq_used(s) - s->seq.readpos;

	if (cnt > len)

		cnt = len;

	memcpy(buf, s->buffer + s->seq.readpos, cnt);
@@ -4514,18 +4514,18 @@ waitagain: 
	trace_access_lock(iter->cpu_file);

	while (trace_find_next_entry_inc(iter) != NULL) {

		enum print_line_t ret;

		int len = iter->seq.seq.len;

		int save_len = iter->seq.seq.len;



		ret = print_trace_line(iter);

		if (ret == TRACE_TYPE_PARTIAL_LINE) {

			/* don't print partial lines */

			iter->seq.seq.len = len;

			iter->seq.seq.len = save_len;

			break;

		}

		if (ret != TRACE_TYPE_NO_CONSUME)

			trace_consume(iter);



		if (iter->seq.seq.len >= cnt)

		if (trace_seq_used(&iter->seq) >= cnt)

			break;



		/*
@@ -4541,7 +4541,7 @@ waitagain: 


	/* Now copy what we have to the user */

	sret = trace_seq_to_user(&iter->seq, ubuf, cnt);

	if (iter->seq.seq.readpos >= iter->seq.seq.len)

	if (iter->seq.seq.readpos >= trace_seq_used(&iter->seq))

		trace_seq_init(&iter->seq);



	/*
@@ -4598,7 +4598,7 @@ tracing_fill_pipe_page(size_t rem, struct trace_iterator *iter) 
			break;

		}



		count = iter->seq.seq.len - save_len;

		count = trace_seq_used(&iter->seq) - save_len;

		if (rem < count) {

			rem = 0;

			iter->seq.seq.len = save_len;
@@ -4682,13 +4682,13 @@ static ssize_t tracing_splice_read_pipe(struct file *filp, 
		/* Copy the data into the page, so we can start over. */

		ret = trace_seq_to_buffer(&iter->seq,

					  page_address(spd.pages[i]),

					  iter->seq.seq.len);

					  trace_seq_used(&iter->seq));

		if (ret < 0) {

			__free_page(spd.pages[i]);

			break;

		}

		spd.partial[i].offset = 0;

		spd.partial[i].len = iter->seq.seq.len;

		spd.partial[i].len = trace_seq_used(&iter->seq);



		trace_seq_init(&iter->seq);

	}
@@ -5689,7 +5689,8 @@ tracing_stats_read(struct file *filp, char __user *ubuf, 
	cnt = ring_buffer_read_events_cpu(trace_buf->buffer, cpu);

	trace_seq_printf(s, "read events: %ld\n", cnt);



	count = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->seq.len);

	count = simple_read_from_buffer(ubuf, count, ppos,

					s->buffer, trace_seq_used(s));



	kfree(s);

kernel/trace/trace_events.c

+6 −3
Original line number Diff line number Diff line
@@ -1044,7 +1044,8 @@ event_filter_read(struct file *filp, char __user *ubuf, size_t cnt, 
	mutex_unlock(&event_mutex);



	if (file)

		r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->seq.len);

		r = simple_read_from_buffer(ubuf, cnt, ppos,

					    s->buffer, trace_seq_used(s));



	kfree(s);
@@ -1210,7 +1211,8 @@ subsystem_filter_read(struct file *filp, char __user *ubuf, size_t cnt, 
	trace_seq_init(s);



	print_subsystem_event_filter(system, s);

	r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->seq.len);

	r = simple_read_from_buffer(ubuf, cnt, ppos,

				    s->buffer, trace_seq_used(s));



	kfree(s);
@@ -1265,7 +1267,8 @@ show_header(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) 
	trace_seq_init(s);



	func(s);

	r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->seq.len);

	r = simple_read_from_buffer(ubuf, cnt, ppos,

				    s->buffer, trace_seq_used(s));



	kfree(s);

kernel/trace/trace_functions_graph.c

+4 −1
Original line number Diff line number Diff line
@@ -1153,6 +1153,9 @@ print_graph_comment(struct trace_seq *s, struct trace_entry *ent, 
			return ret;

	}



	if (trace_seq_has_overflowed(s))

		goto out;



	/* Strip ending newline */

	if (s->buffer[s->seq.len - 1] == '\n') {

		s->buffer[s->seq.len - 1] = '\0';
@@ -1160,7 +1163,7 @@ print_graph_comment(struct trace_seq *s, struct trace_entry *ent, 
	}



	trace_seq_puts(s, " */\n");



 out:

	return trace_handle_return(s);

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE