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Revert "perf: Disallow mis-matched inherited group reads"

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This reverts commit a714491fa9 which is
commit 32671e3799ca2e4590773fd0e63aaa4229e50c06 upstream.

It breaks the android ABI and if this is needed in the future, can be
brought back in an abi-safe way.

Bug: 161946584
Change-Id: Ia00890aeeef6153c7f3462a2a2189149734ac28a
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Greg Kroah-Hartman 2023-10-26 10:18:26 +00:00
parent 1427d077a0
commit 9c20bfd64d
2 changed files with 6 additions and 34 deletions
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1
include/linux/perf_event.h
View file

@ -597,7 +597,6 @@ struct perf_event {
/* The cumulative AND of all event_caps for events in this group. */
int group_caps;
unsigned int group_generation;
struct perf_event *group_leader;
struct pmu *pmu;
void *pmu_private;

39
kernel/events/core.c
View file

@ -1848,7 +1848,6 @@ 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);
@ -1919,7 +1918,6 @@ static void perf_group_detach(struct perf_event *event)
if (event->group_leader != event) {
list_del_init(&event->sibling_list);
event->group_leader->nr_siblings--;
event->group_leader->group_generation++;
goto out;
}
@ -4738,7 +4736,7 @@ 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, *parent;
struct perf_event *sub;
unsigned long flags;
int n = 1; /* skip @nr */
int ret;
@ -4748,33 +4746,6 @@ 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
@ -4804,9 +4775,8 @@ 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 ret;
return 0;
}
static int perf_read_group(struct perf_event *event,
@ -4825,6 +4795,10 @@ 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);
@ -11613,7 +11587,6 @@ static int inherit_group(struct perf_event *parent_event,
if (IS_ERR(child_ctr))
return PTR_ERR(child_ctr);
}
leader->group_generation = parent_event->group_generation;
return 0;
}