From e8ec9bfedd41f46bf588b555c86bb0aab4fadda3 Mon Sep 17 00:00:00 2001 From: John Dias <joaodias@google.com> Date: Wed, 9 Nov 2016 11:03:57 -0800 Subject: [PATCH] perf: don't leave group_entry on sibling list (use-after-free) When perf_group_detach is called on a group leader, it should empty its sibling list. Otherwise, when a sibling is later deallocated, list_del_event() removes the sibling's group_entry from its current list, which can be the now-deallocated group leader's sibling list (use-after-free bug). Bug: 32402548 Change-Id: I99f6bc97c8518df1cb0035814368012ba72ab1f1 Signed-off-by: John Dias <joaodias@google.com> --- kernel/events/core.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index 32b7ca93a75a..d8a33cbc9fe3 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1228,10 +1228,17 @@ static void perf_group_detach(struct perf_event *event) * If this was a group event with sibling events then * upgrade the siblings to singleton events by adding them * to whatever list we are on. + * If this isn't on a list, make sure we still remove the sibling's + * group_entry from this sibling_list; otherwise, when that sibling + * is later deallocated, it will try to remove itself from this + * sibling_list, which may well have been deallocated already, + * resulting in a use-after-free. */ list_for_each_entry_safe(sibling, tmp, &event->sibling_list, group_entry) { if (list) list_move_tail(&sibling->group_entry, list); + else + list_del_init(&sibling->group_entry); sibling->group_leader = sibling; /* Inherit group flags from the previous leader */ -- GitLab