1 files changed, 30 insertions, 2 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 3472bb1a070c..8e81a9860a0d 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -145,7 +145,8 @@ static struct srcu_struct pmus_srcu;
  */
 int sysctl_perf_event_paranoid __read_mostly = 1;
 
-int sysctl_perf_event_mlock __read_mostly = 512; /* 'free' kb per user */
+/* Minimum for 512 kiB + 1 user control page */
+int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */
 
 /*
  * max perf event sample rate
@@ -363,6 +364,7 @@ void perf_cgroup_switch(struct task_struct *task, int mode)
                         }
 
                         if (mode & PERF_CGROUP_SWIN) {
+                                WARN_ON_ONCE(cpuctx->cgrp);
                                 /* set cgrp before ctxsw in to
                                  * allow event_filter_match() to not
                                  * have to pass task around
@@ -941,6 +943,7 @@ static void perf_group_attach(struct perf_event *event)
 static void
 list_del_event(struct perf_event *event, struct perf_event_context *ctx)
 {
+        struct perf_cpu_context *cpuctx;
         /*
          * We can have double detach due to exit/hot-unplug + close.
          */
@@ -949,8 +952,17 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
 
         event->attach_state &= ~PERF_ATTACH_CONTEXT;
 
-        if (is_cgroup_event(event))
+        if (is_cgroup_event(event)) {
                 ctx->nr_cgroups--;
+                cpuctx = __get_cpu_context(ctx);
+                /*
+                 * if there are no more cgroup events
+                 * then cler cgrp to avoid stale pointer
+                 * in update_cgrp_time_from_cpuctx()
+                 */
+                if (!ctx->nr_cgroups)
+                        cpuctx->cgrp = NULL;
+        }
 
         ctx->nr_events--;
         if (event->attr.inherit_stat)
@@ -2412,6 +2424,14 @@ static void perf_event_enable_on_exec(struct perf_event_context *ctx)
         if (!ctx || !ctx->nr_events)
                 goto out;
 
+        /*
+         * We must ctxsw out cgroup events to avoid conflict
+         * when invoking perf_task_event_sched_in() later on
+         * in this function. Otherwise we end up trying to
+         * ctxswin cgroup events which are already scheduled
+         * in.
+         */
+        perf_cgroup_sched_out(current);
         task_ctx_sched_out(ctx, EVENT_ALL);
 
         raw_spin_lock(&ctx->lock);
@@ -2436,6 +2456,9 @@ static void perf_event_enable_on_exec(struct perf_event_context *ctx)
 
         raw_spin_unlock(&ctx->lock);
 
+        /*
+         * Also calls ctxswin for cgroup events, if any:
+         */
         perf_event_context_sched_in(ctx, ctx->task);
 out:
         local_irq_restore(flags);
@@ -6520,6 +6543,11 @@ SYSCALL_DEFINE5(perf_event_open,
                 goto err_alloc;
         }
 
+        if (task) {
+                put_task_struct(task);
+                task = NULL;
+        }
+
         /*
          * Look up the group leader (we will attach this event to it):
          */