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Revert "perf: Fix event leak upon exec and file release"

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This reverts commit ed2c202dac which is
commit 3a5465418f5fd970e86a86c7f4075be262682840 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I29cfc492dd3ef6c7a9ebc2aa28d238f392a48ce6
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Greg Kroah-Hartman
2024-09-12 06:35:25 +00:00
parent e3e84f6205
commit 00364d577d
2 changed files with 4 additions and 35 deletions
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1
include/linux/perf_event.h
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@@ -767,7 +767,6 @@ struct perf_event {
struct irq_work pending_irq;
struct callback_head pending_task;
unsigned int pending_work;
struct rcuwait pending_work_wait;
atomic_t event_limit;

38
kernel/events/core.c
View File

@@ -2320,6 +2320,7 @@ event_sched_out(struct perf_event *event,
if (state != PERF_EVENT_STATE_OFF &&
!event->pending_work &&
!task_work_add(current, &event->pending_task, TWA_RESUME)) {
WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount));
event->pending_work = 1;
} else {
local_dec(&event->ctx->nr_pending);
@@ -5004,35 +5005,9 @@ static bool exclusive_event_installable(struct perf_event *event,
static void perf_addr_filters_splice(struct perf_event *event,
struct list_head *head);
static void perf_pending_task_sync(struct perf_event *event)
{
struct callback_head *head = &event->pending_task;
if (!event->pending_work)
return;
/*
* If the task is queued to the current task's queue, we
* obviously can't wait for it to complete. Simply cancel it.
*/
if (task_work_cancel(current, head)) {
event->pending_work = 0;
local_dec(&event->ctx->nr_pending);
return;
}
/*
* All accesses related to the event are within the same
* non-preemptible section in perf_pending_task(). The RCU
* grace period before the event is freed will make sure all
* those accesses are complete by then.
*/
rcuwait_wait_event(&event->pending_work_wait, !event->pending_work, TASK_UNINTERRUPTIBLE);
}
static void _free_event(struct perf_event *event)
{
irq_work_sync(&event->pending_irq);
perf_pending_task_sync(event);
unaccount_event(event);
@@ -6662,28 +6637,24 @@ static void perf_pending_task(struct callback_head *head)
struct perf_event *event = container_of(head, struct perf_event, pending_task);
int rctx;
/*
* All accesses to the event must belong to the same implicit RCU read-side
* critical section as the ->pending_work reset. See comment in
* perf_pending_task_sync().
*/
preempt_disable_notrace();
/*
* If we 'fail' here, that's OK, it means recursion is already disabled
* and we won't recurse 'further'.
*/
preempt_disable_notrace();
rctx = perf_swevent_get_recursion_context();
if (event->pending_work) {
event->pending_work = 0;
perf_sigtrap(event);
local_dec(&event->ctx->nr_pending);
rcuwait_wake_up(&event->pending_work_wait);
}
if (rctx >= 0)
perf_swevent_put_recursion_context(rctx);
preempt_enable_notrace();
put_event(event);
}
#ifdef CONFIG_GUEST_PERF_EVENTS
@@ -11792,7 +11763,6 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
init_waitqueue_head(&event->waitq);
init_irq_work(&event->pending_irq, perf_pending_irq);
init_task_work(&event->pending_task, perf_pending_task);
rcuwait_init(&event->pending_work_wait);
mutex_init(&event->mmap_mutex);
raw_spin_lock_init(&event->addr_filters.lock);