[PATCH 5.5 352/367] perf/cgroups: Install cgroup events to correct cpuctx

Greg Kroah-Hartman
2020-02-10T12:47:23Z

From: Song Liu <songliubraving@fb.com>

commit 07c5972951f088094776038006a0592a46d14bbc upstream.

cgroup events are always installed in the cpuctx. However, when it is not
installed via IPI, list_update_cgroup_event() adds it to cpuctx of current
CPU, which triggers list corruption:

[] list_add double add: new=ffff888ff7cf0db0, prev=ffff888ff7ce82f0, next=ffff888ff7cf0db0.

To reproduce this, we can simply run:

# perf stat -e cs -a &
# perf stat -e cs -G anycgroup

Fix this by installing it to cpuctx that contains event->ctx, and the
proper cgrp_cpuctx_list.

Fixes: db0503e4f675 ("perf/core: Optimize perf_install_in_event()")
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200122195027.2112449-1-songliubraving@fb.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/events/core.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -951,9 +951,9 @@ list_update_cgroup_event(struct perf_eve

/*
* Because cgroup events are always per-cpu events,
- * this will always be called from the right CPU.
+ * @ctx == &cpuctx->ctx.
*/
- cpuctx = __get_cpu_context(ctx);
+ cpuctx = container_of(ctx, struct perf_cpu_context, ctx);

/*
* Since setting cpuctx->cgrp is conditional on the current @cgrp
@@ -979,7 +979,8 @@ list_update_cgroup_event(struct perf_eve

cpuctx_entry = &cpuctx->cgrp_cpuctx_entry;
if (add)
- list_add(cpuctx_entry, this_cpu_ptr(&cgrp_cpuctx_list));
+ list_add(cpuctx_entry,
+ per_cpu_ptr(&cgrp_cpuctx_list, event->cpu));
else
list_del(cpuctx_entry);
}