Messages in this thread Patch in this message | | | Date | Wed, 3 Feb 2016 23:57:53 -0800 | From | tip-bot for Adrian Hunter <> | Subject | [tip:perf/urgent] perf tools: Fix thread lifetime related segfaut in intel_pt |
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Commit-ID: 3a4acda1ecbd290973de08250d7dcdfaf5b2fe0f Gitweb: http://git.kernel.org/tip/3a4acda1ecbd290973de08250d7dcdfaf5b2fe0f Author: Adrian Hunter <adrian.hunter@intel.com> AuthorDate: Mon, 1 Feb 2016 03:21:04 +0000 Committer: Arnaldo Carvalho de Melo <acme@redhat.com> CommitDate: Tue, 2 Feb 2016 12:51:11 -0300
perf tools: Fix thread lifetime related segfaut in intel_pt
intel_pt_process_auxtrace_info() creates a pt->unknown_thread thread that eventually needs to be freed by the last thread__put() on it, when its refcount hits zero, which may happen in intel_pt_process_auxtrace_info() error handling path and triggers the following segfault, which would happen as well at intel_pt_free, when tools using this intel_pt codebase frees up resources:
# perf record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls 0 a anaconda-ks.cfg bin perf.data perf.data.old perf-f23-bringup.todo [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.217 MB perf.data ] # # perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs Samples for 'instructions:u' event do not have IREGS attribute set. Cannot print 'iregs' field. intel_pt_synth_events: failed to synthesize 'instructions' event type Segmentation fault (core dumped) #
The problem is: there's a union in 'struct thread' combines a list_head and a rb_node. The standard life cycle of a thread is: init rb_node in the constructor, insert it into machine->threads rbtree using rb_node, move it to machine->dead_threads using list_head, clean in the last thread__put: list_del_init(&thread->node).
In the above command, it clean a thread before adding it into list, causes the above segfault.
Since pt->unknown_thread will never live in an rbtree, initialize its list node so that when list_del_init() is done on it we don't segfault.
After this patch:
# perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs Samples for 'instructions:u' event do not have IREGS attribute set. Cannot print 'iregs' field. intel_pt_synth_events: failed to synthesize 'instructions' event type 0x248 [0x88]: failed to process type: 70 #
Reported-by: Tong Zhang <ztong@vt.edu> Reported-by: Wang Nan <wangnan0@huawei.com> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Link: http://lkml.kernel.org/r/1454296865-19749-1-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> --- tools/perf/util/intel-pt.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c index 81a2eb7..05d8158 100644 --- a/tools/perf/util/intel-pt.c +++ b/tools/perf/util/intel-pt.c @@ -2068,6 +2068,15 @@ int intel_pt_process_auxtrace_info(union perf_event *event, err = -ENOMEM; goto err_free_queues; } + + /* + * Since this thread will not be kept in any rbtree not in a + * list, initialize its list node so that at thread__put() the + * current thread lifetime assuption is kept and we don't segfault + * at list_del_init(). + */ + INIT_LIST_HEAD(&pt->unknown_thread->node); + err = thread__set_comm(pt->unknown_thread, "unknown", 0); if (err) goto err_delete_thread;
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