From 63e35b25d6b5c3136d22ef249dbbf96716aa08bf Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 25 Mar 2009 12:30:24 +0100 Subject: [PATCH] perf_counter: sanity check on the output API Ensure we never write more than we said we would. Signed-off-by: Peter Zijlstra Cc: Paul Mackerras Cc: Mike Galbraith Cc: Arjan van de Ven Cc: Wu Fengguang Orig-LKML-Reference: <20090325113316.921433024@chello.nl> Signed-off-by: Ingo Molnar --- kernel/perf_counter.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index d76e3112d386..7669afe82cc7 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -1422,6 +1422,7 @@ struct perf_output_handle { struct perf_counter *counter; struct perf_mmap_data *data; unsigned int offset; + unsigned int head; int wakeup; }; @@ -1447,6 +1448,7 @@ static int perf_output_begin(struct perf_output_handle *handle, handle->counter = counter; handle->data = data; handle->offset = offset; + handle->head = head; handle->wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT); return 0; @@ -1485,6 +1487,8 @@ static void perf_output_copy(struct perf_output_handle *handle, } while (len); handle->offset = offset; + + WARN_ON_ONCE(handle->offset > handle->head); } #define perf_output_put(handle, x) \ -- 2.20.1