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perf/core: Detach event groups during remove_on_exec

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[ Upstream commit 037a3c43ed ]

perf_event_remove_on_exec() removes events by calling
perf_event_exit_event(). For top-level events, this removes the event from
the context with DETACH_EXIT only.

This can leave inconsistent group state when a removed event is a group
leader and the group contains siblings without remove_on_exec. If the group
was active, the surviving siblings can remain active and attached to the
removed leader's sibling list, but are no longer represented by a valid
group leader on the PMU context active lists.

A later close of the removed leader uses DETACH_GROUP and can promote the
still-active siblings from this stale group state. The next schedule-in can
then add an already-linked active_list entry again, corrupting the PMU
context active list.

With DEBUG_LIST enabled, this is caught as a list_add double-add in
merge_sched_in().

Fix this by detaching group relationships when remove_on_exec removes an
event. This preserves the existing task-exit and revoke behavior, while
ensuring surviving siblings are ungrouped before the removed event leaves
the context.

Fixes: 2e498d0a74 ("perf: Add support for event removal on exec")
Signed-off-by: Taeyang Lee <0wn@theori.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/ai65GgZcC0LAlWLG@Taeyangs-MacBook-Pro.local
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Taeyang Lee
2026-07-24 16:02:39 +02:00
committed by Greg Kroah-Hartman
parent a44343fe23
commit 4cdb1b3ab9
1 changed files with 8 additions and 6 deletions
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kernel/events/core.c
+8 -6
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@@ -4449,7 +4449,8 @@ out:
static void perf_remove_from_owner(struct perf_event *event);
static void perf_event_exit_event(struct perf_event *event,
struct perf_event_context *ctx);
struct perf_event_context *ctx,
unsigned long detach_flags);
/*
* Removes all events from the current task that have been marked
@@ -4476,7 +4477,7 @@ static void perf_event_remove_on_exec(struct perf_event_context *ctx)
modified = true;
perf_event_exit_event(event, ctx);
perf_event_exit_event(event, ctx, DETACH_GROUP);
}
raw_spin_lock_irqsave(&ctx->lock, flags);
@@ -13230,10 +13231,11 @@ static void sync_child_event(struct perf_event *child_event)
}
static void
perf_event_exit_event(struct perf_event *event, struct perf_event_context *ctx)
perf_event_exit_event(struct perf_event *event,
struct perf_event_context *ctx,
unsigned long detach_flags)
{
struct perf_event *parent_event = event->parent;
unsigned long detach_flags = 0;
if (parent_event) {
/*
@@ -13248,7 +13250,7 @@ perf_event_exit_event(struct perf_event *event, struct perf_event_context *ctx)
* Do destroy all inherited groups, we don't care about those
* and being thorough is better.
*/
detach_flags = DETACH_GROUP | DETACH_CHILD;
detach_flags |= DETACH_GROUP | DETACH_CHILD;
mutex_lock(&parent_event->child_mutex);
}
@@ -13328,7 +13330,7 @@ static void perf_event_exit_task_context(struct task_struct *child)
perf_event_task(child, child_ctx, 0);
list_for_each_entry_safe(child_event, next, &child_ctx->event_list, event_entry)
perf_event_exit_event(child_event, child_ctx);
perf_event_exit_event(child_event, child_ctx, 0);
mutex_unlock(&child_ctx->mutex);