diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 3423fd376f87653de63348828e88e5eea8b5f6a6..e93a4ea6f88add004fd3024a6a48b516f513761d 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -776,7 +776,7 @@ struct perf_event { struct list_head sb_list; #endif /* CONFIG_PERF_EVENTS */ - CK_KABI_RESERVE(1) + CK_KABI_USE_SPLIT(1, unsigned int group_generation) CK_KABI_RESERVE(2) CK_KABI_RESERVE(3) CK_KABI_RESERVE(4) diff --git a/kernel/events/core.c b/kernel/events/core.c index 6b881952b377ff38bbbbeabe7212b4473d72c703..05647663ddd9add91d7b1cc283b5fae4b44ec4ad 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1966,6 +1966,7 @@ static void perf_group_attach(struct perf_event *event) list_add_tail(&event->sibling_list, &group_leader->sibling_list); group_leader->nr_siblings++; + group_leader->group_generation++; perf_event__header_size(group_leader); @@ -2158,6 +2159,7 @@ static void perf_group_detach(struct perf_event *event) if (leader != event) { list_del_init(&event->sibling_list); event->group_leader->nr_siblings--; + event->group_leader->group_generation++; goto out; } @@ -5121,7 +5123,7 @@ static int __perf_read_group_add(struct perf_event *leader, u64 read_format, u64 *values) { struct perf_event_context *ctx = leader->ctx; - struct perf_event *sub; + struct perf_event *sub, *parent; unsigned long flags; int n = 1; /* skip @nr */ int ret; @@ -5131,6 +5133,33 @@ static int __perf_read_group_add(struct perf_event *leader, return ret; raw_spin_lock_irqsave(&ctx->lock, flags); + /* + * Verify the grouping between the parent and child (inherited) + * events is still in tact. + * + * Specifically: + * - leader->ctx->lock pins leader->sibling_list + * - parent->child_mutex pins parent->child_list + * - parent->ctx->mutex pins parent->sibling_list + * + * Because parent->ctx != leader->ctx (and child_list nests inside + * ctx->mutex), group destruction is not atomic between children, also + * see perf_event_release_kernel(). Additionally, parent can grow the + * group. + * + * Therefore it is possible to have parent and child groups in a + * different configuration and summing over such a beast makes no sense + * what so ever. + * + * Reject this. + */ + parent = leader->parent; + if (parent && + (parent->group_generation != leader->group_generation || + parent->nr_siblings != leader->nr_siblings)) { + ret = -ECHILD; + goto unlock; + } /* * Since we co-schedule groups, {enabled,running} times of siblings @@ -5160,8 +5189,9 @@ static int __perf_read_group_add(struct perf_event *leader, values[n++] = primary_event_id(sub); } +unlock: raw_spin_unlock_irqrestore(&ctx->lock, flags); - return 0; + return ret; } static int perf_read_group(struct perf_event *event, @@ -5180,10 +5210,6 @@ static int perf_read_group(struct perf_event *event, values[0] = 1 + leader->nr_siblings; - /* - * By locking the child_mutex of the leader we effectively - * lock the child list of all siblings.. XXX explain how. - */ mutex_lock(&leader->child_mutex); ret = __perf_read_group_add(leader, read_format, values); @@ -12870,6 +12896,8 @@ static int inherit_group(struct perf_event *parent_event, !perf_get_aux_event(child_ctr, leader)) return -EINVAL; } + if (leader) + leader->group_generation = parent_event->group_generation; return 0; }