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tracing: ring-buffer: Fix to check event length before using

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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: 5f3b6e839f ("ring-buffer: Validate boot range memory events")
Link: https://patch.msgid.link/177123421541.142205.9414352170164678966.stgit@devnote2
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu (Google) 2026-02-16 18:30:15 +09:00 • committed by Steven Rostedt (Google)
parent f154777940
commit 912b0ee248
1 changed files with 5 additions and 1 deletions
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6
kernel/trace/ring_buffer.c
View file

@ -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) {