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authorMark Rutland <mark.rutland@arm.com>2018-03-16 12:51:40 +0000
committerThomas Gleixner <tglx@linutronix.de>2018-03-16 20:44:32 +0100
commit24868367cdcac447232ebcb2aa06e1bf91291586 (patch)
treee1202c529ae0cf3a8bf34ebd1fc3f14a79845635 /kernel/events
parentedb39592a5877bd91b2e6ee15194268f35b04892 (diff)
perf/core: Clear sibling list of detached events
When perf_group_dettach() is called on a group leader, it updates each sibling's group_leader field to point to that sibling, effectively upgrading each siblnig to a group leader. After perf_group_detach has completed, the caller may free the leader event. We only remove siblings from the group leader's sibling_list when the leader has a non-empty group_node. This was fine prior to commit: 8343aae66167df67 ("perf/core: Remove perf_event::group_entry") ... as the sibling's sibling_list would be empty. However, now that we use the sibling_list field as both the list head and the list entry, this leaves each sibling with a non-empty sibling list, including the stale leader event. If perf_group_detach() is subsequently called on a sibling, it will appear to be a group leader, and we'll walk the sibling_list, potentially dereferencing these stale events. In 0day testing, this has been observed to result in kernel panics. Let's avoid this by always removing siblings from the sibling list when we promote them to leaders. Fixes: 8343aae66167df67 ("perf/core: Remove perf_event::group_entry") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: vincent.weaver@maine.edu Cc: Peter Zijlstra <peterz@infradead.org> Cc: torvalds@linux-foundation.org Cc: Alexey Budankov <alexey.budankov@linux.intel.com> Cc: valery.cherepennikov@intel.com Cc: linux-tip-commits@vger.kernel.org Cc: eranian@google.com Cc: acme@redhat.com Cc: alexander.shishkin@linux.intel.com Cc: davidcc@google.com Cc: kan.liang@intel.com Cc: Dmitry.Prohorov@intel.com Cc: Jiri Olsa <jolsa@redhat.com> Link: https://lkml.kernel.org/r/20180316131741.3svgr64yibc6vsid@lakrids.cambridge.arm.com
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4d7a460d6669..2776a660db15 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1906,12 +1906,12 @@ static void perf_group_detach(struct perf_event *event)
list_for_each_entry_safe(sibling, tmp, &event->sibling_list, sibling_list) {
sibling->group_leader = sibling;
+ list_del_init(&sibling->sibling_list);
/* Inherit group flags from the previous leader */
sibling->group_caps = event->group_caps;
if (!RB_EMPTY_NODE(&event->group_node)) {
- list_del_init(&sibling->sibling_list);
add_event_to_groups(sibling, event->ctx);
if (sibling->state == PERF_EVENT_STATE_ACTIVE) {