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

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This reverts commit 63eafbb6b3.

Keeps the ABI stable by taking advantage of a hole in the structure!

Bug: 307236803
Change-Id: Ic5f7ebeb3a9b13afdb3bfff7e54c4a93b863dab6
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Greg Kroah-Hartman 2024-01-31 01:14:23 +00:00 committed by Treehugger Robot
parent 067a03c44e
commit 7cbad58851
3 changed files with 43 additions and 6 deletions
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7
android/abi_gki_aarch64.stg
View File

@ -97923,6 +97923,12 @@ member {
type_id: 0x6720d32f
offset: 768
}
member {
id: 0x16cb0979
name: "group_generation"
type_id: 0x4585663f
offset: 1120
}
member {
id: 0x0f81c321
name: "group_index"
@ -246740,6 +246746,7 @@ struct_union {
member_id: 0xb826ad15
member_id: 0xf0897d29
member_id: 0x26e58ea7
member_id: 0x16cb0979
member_id: 0xc397b990
member_id: 0x933349d1
member_id: 0xbadfff7b

3
include/linux/perf_event.h
View File

@ -694,6 +694,9 @@ struct perf_event {
/* The cumulative AND of all event_caps for events in this group. */
int group_caps;
#ifndef __GENKSYMS__
unsigned int group_generation;
#endif
struct perf_event *group_leader;
struct pmu *pmu;
void *pmu_private;

39
kernel/events/core.c
View File

@ -1977,6 +1977,7 @@ 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);
@ -2171,6 +2172,7 @@ 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;
}
@ -5295,7 +5297,7 @@ 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;
@ -5305,6 +5307,33 @@ 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
@ -5338,8 +5367,9 @@ static int __perf_read_group_add(struct perf_event *leader,
values[n++] = atomic64_read(&sub->lost_samples);
}
unlock:
raw_spin_unlock_irqrestore(&ctx->lock, flags);
return 0;
return ret;
}
static int perf_read_group(struct perf_event *event,
@ -5358,10 +5388,6 @@ 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);
@ -13268,6 +13294,7 @@ static int inherit_group(struct perf_event *parent_event,
!perf_get_aux_event(child_ctr, leader))
return -EINVAL;
}
leader->group_generation = parent_event->group_generation;
return 0;
}