From 197eecb6ecae0b04bd694432f640ff75597fed9c Mon Sep 17 00:00:00 2001 From: Leo Yan Date: Sat, 5 Jun 2021 13:29:57 +0800 Subject: [PATCH] perf session: Correct buffer copying when peeking events When peeking an event, it has a short path and a long path. The short path uses the session pointer "one_mmap_addr" to directly fetch the event; and the long path needs to read out the event header and the following event data from file and fill into the buffer pointer passed through the argument "buf". The issue is in the long path that it copies the event header and event data into the same destination address which pointer "buf", this means the event header is overwritten. We are just lucky to run into the short path in most cases, so we don't hit the issue in the long path. This patch adds the offset "hdr_sz" to the pointer "buf" when copying the event data, so that it can reserve the event header which can be used properly by its caller. Fixes: 5a52f33adf02 ("perf session: Add perf_session__peek_event()") Signed-off-by: Leo Yan Acked-by: Adrian Hunter Acked-by: Jiri Olsa Cc: Alexander Shishkin Cc: Kan Liang Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/20210605052957.1070720-1-leo.yan@linaro.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/session.c | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c index 106b3d60881a..e59242c361ce 100644 --- a/tools/perf/util/session.c +++ b/tools/perf/util/session.c @@ -1723,6 +1723,7 @@ int perf_session__peek_event(struct perf_session *session, off_t file_offset, if (event->header.size < hdr_sz || event->header.size > buf_sz) return -1; + buf += hdr_sz; rest = event->header.size - hdr_sz; if (readn(fd, buf, rest) != (ssize_t)rest)