From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnaldo Carvalho de Melo Subject: [PATCH 2/8] perf mmap: Fix accessing unmapped mmap in perf_mmap__read_done() Date: Wed, 28 Mar 2018 15:49:13 -0300 Message-ID: <20180328184919.32287-3-acme@kernel.org> References: <20180328184919.32287-1-acme@kernel.org> Return-path: In-Reply-To: <20180328184919.32287-1-acme@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Kan Liang , Jiri Olsa , Namhyung Kim , Wang Nan , Arnaldo Carvalho de Melo List-Id: linux-perf-users.vger.kernel.org From: Kan Liang There is a segmentation fault when running 'perf trace'. For example: [root@jouet e]# perf trace -e *chdir -o /tmp/bla perf report --ignore-vmlinux -i ../perf.data The perf_mmap__consume() could unmap the mmap. It needs to check the refcnt in perf_mmap__read_done(). Reported-by: Arnaldo Carvalho de Melo Signed-off-by: Kan Liang Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Fixes: ee023de05f35 ("perf mmap: Introduce perf_mmap__read_done()") Link: http://lkml.kernel.org/r/1522071729-16776-1-git-send-email-kan.liang@linux.intel.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/mmap.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c index 38ca3ffb9d61..f6cfc52ff1fe 100644 --- a/tools/perf/util/mmap.c +++ b/tools/perf/util/mmap.c @@ -317,5 +317,11 @@ int perf_mmap__push(struct perf_mmap *md, void *to, */ void perf_mmap__read_done(struct perf_mmap *map) { + /* + * Check if event was unmapped due to a POLLHUP/POLLERR. + */ + if (!refcount_read(&map->refcnt)) + return; + map->prev = perf_mmap__read_head(map); } -- 2.14.3