Commit 912b0ee2 authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google) Committed by Steven Rostedt (Google)
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tracing: ring-buffer: Fix to check event length before using 

Check the event length before adding it for accessing next index in
rb_read_data_buffer(). Since this function is used for validating
possibly broken ring buffers, the length of the event could be broken.
In that case, the new event (e + len) can point a wrong address.
To avoid invalid memory access at boot, check whether the length of
each event is in the possible range before using it.

Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: 5f3b6e83 ("ring-buffer: Validate boot range memory events")
Link: https://patch.msgid.link/177123421541.142205.9414352170164678966.stgit@devnote2


Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent f1547779

kernel/trace/ring_buffer.c

+5 −1
Original line number Diff line number Diff line
@@ -1849,6 +1849,7 @@ static int rb_read_data_buffer(struct buffer_data_page *dpage, int tail, int cpu 
	struct ring_buffer_event *event;

	u64 ts, delta;

	int events = 0;

	int len;

	int e;



	*delta_ptr = 0;
@@ -1856,9 +1857,12 @@ static int rb_read_data_buffer(struct buffer_data_page *dpage, int tail, int cpu 


	ts = dpage->time_stamp;



	for (e = 0; e < tail; e += rb_event_length(event)) {

	for (e = 0; e < tail; e += len) {



		event = (struct ring_buffer_event *)(dpage->data + e);

		len = rb_event_length(event);

		if (len <= 0 || len > tail - e)

			return -1;



		switch (event->type_len) {