perf_counter: Fix race in counter initialization
We need the PID namespace and counter ID available when the counter overflows and we need to generate a sample event. [ Impact: fix kernel crash with high-frequency sampling ] Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: John Kacur <jkacur@redhat.com> LKML-Reference: <new-submission> [ fixed a further crash and cleaned up the initialization a bit ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
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1 changed files with 14 additions and 11 deletions
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@ -48,6 +48,8 @@ int sysctl_perf_counter_priv __read_mostly; /* do we need to be privileged */
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int sysctl_perf_counter_mlock __read_mostly = 512; /* 'free' kb per user */
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int sysctl_perf_counter_limit __read_mostly = 100000; /* max NMIs per second */
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static atomic64_t perf_counter_id;
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/*
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* Lock for (sysadmin-configurable) counter reservations:
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*/
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@ -3351,14 +3353,18 @@ perf_counter_alloc(struct perf_counter_attr *attr,
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mutex_init(&counter->mmap_mutex);
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counter->cpu = cpu;
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counter->cpu = cpu;
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counter->attr = *attr;
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counter->group_leader = group_leader;
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counter->pmu = NULL;
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counter->ctx = ctx;
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counter->oncpu = -1;
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counter->group_leader = group_leader;
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counter->pmu = NULL;
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counter->ctx = ctx;
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counter->oncpu = -1;
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counter->ns = get_pid_ns(current->nsproxy->pid_ns);
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counter->id = atomic64_inc_return(&perf_counter_id);
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counter->state = PERF_COUNTER_STATE_INACTIVE;
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counter->state = PERF_COUNTER_STATE_INACTIVE;
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if (attr->disabled)
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counter->state = PERF_COUNTER_STATE_OFF;
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@ -3402,6 +3408,8 @@ done:
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err = PTR_ERR(pmu);
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if (err) {
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if (counter->ns)
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put_pid_ns(counter->ns);
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kfree(counter);
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return ERR_PTR(err);
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}
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@ -3419,8 +3427,6 @@ done:
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return counter;
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}
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static atomic64_t perf_counter_id;
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/**
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* sys_perf_counter_open - open a performance counter, associate it to a task/cpu
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*
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@ -3515,9 +3521,6 @@ SYSCALL_DEFINE5(perf_counter_open,
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list_add_tail(&counter->owner_entry, ¤t->perf_counter_list);
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mutex_unlock(¤t->perf_counter_mutex);
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counter->ns = get_pid_ns(current->nsproxy->pid_ns);
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counter->id = atomic64_inc_return(&perf_counter_id);
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fput_light(counter_file, fput_needed2);
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out_fput:
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