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Commit a2ed7b29 authored by Song Liu's avatar Song Liu Committed by Greg Kroah-Hartman
Browse files

perf: Fix list corruption in perf_cgroup_switch() 



commit 5f4e5ce638e6a490b976ade4a40017b40abb2da0 upstream.

There's list corruption on cgrp_cpuctx_list. This happens on the
following path:

  perf_cgroup_switch: list_for_each_entry(cgrp_cpuctx_list)
      cpu_ctx_sched_in
         ctx_sched_in
            ctx_pinned_sched_in
              merge_sched_in
                  perf_cgroup_event_disable: remove the event from the list

Use list_for_each_entry_safe() to allow removing an entry during
iteration.

Fixes: 058fe1c0 ("perf/core: Make cgroup switch visit only cpuctxs with cgroup events")
Signed-off-by: default avatarSong Liu <song@kernel.org>
Reviewed-by: default avatarRik van Riel <riel@surriel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220204004057.2961252-1-song@kernel.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f79cbf75

kernel/events/core.c

+2 −2
Original line number Diff line number Diff line
@@ -799,7 +799,7 @@ static DEFINE_PER_CPU(struct list_head, cgrp_cpuctx_list); 
 */

static void perf_cgroup_switch(struct task_struct *task, int mode)

{

	struct perf_cpu_context *cpuctx;

	struct perf_cpu_context *cpuctx, *tmp;

	struct list_head *list;

	unsigned long flags;
@@ -810,7 +810,7 @@ static void perf_cgroup_switch(struct task_struct *task, int mode) 
	local_irq_save(flags);



	list = this_cpu_ptr(&cgrp_cpuctx_list);

	list_for_each_entry(cpuctx, list, cgrp_cpuctx_entry) {

	list_for_each_entry_safe(cpuctx, tmp, list, cgrp_cpuctx_entry) {

		WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0);



		perf_ctx_lock(cpuctx, cpuctx->task_ctx);