From a96bbc16418bc691317f265d6bf98ba941ca9c1a Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 3 Jun 2009 14:01:36 +0200 Subject: [PATCH] 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 Signed-off-by: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Corey Ashford Cc: Marcelo Tosatti Cc: Arnaldo Carvalho de Melo Cc: Thomas Gleixner Cc: John Kacur LKML-Reference: [ fixed a further crash and cleaned up the initialization a bit ] Signed-off-by: Ingo Molnar --- kernel/perf_counter.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 317cef7..ab44554 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -48,6 +48,8 @@ int sysctl_perf_counter_priv __read_mostly; /* do we need to be privileged */ int sysctl_perf_counter_mlock __read_mostly = 512; /* 'free' kb per user */ int sysctl_perf_counter_limit __read_mostly = 100000; /* max NMIs per second */ +static atomic64_t perf_counter_id; + /* * Lock for (sysadmin-configurable) counter reservations: */ @@ -3351,14 +3353,18 @@ perf_counter_alloc(struct perf_counter_attr *attr, mutex_init(&counter->mmap_mutex); - counter->cpu = cpu; + counter->cpu = cpu; counter->attr = *attr; - counter->group_leader = group_leader; - counter->pmu = NULL; - counter->ctx = ctx; - counter->oncpu = -1; + counter->group_leader = group_leader; + counter->pmu = NULL; + counter->ctx = ctx; + counter->oncpu = -1; + + counter->ns = get_pid_ns(current->nsproxy->pid_ns); + counter->id = atomic64_inc_return(&perf_counter_id); + + counter->state = PERF_COUNTER_STATE_INACTIVE; - counter->state = PERF_COUNTER_STATE_INACTIVE; if (attr->disabled) counter->state = PERF_COUNTER_STATE_OFF; @@ -3402,6 +3408,8 @@ done: err = PTR_ERR(pmu); if (err) { + if (counter->ns) + put_pid_ns(counter->ns); kfree(counter); return ERR_PTR(err); } @@ -3419,8 +3427,6 @@ done: return counter; } -static atomic64_t perf_counter_id; - /** * sys_perf_counter_open - open a performance counter, associate it to a task/cpu * @@ -3515,9 +3521,6 @@ SYSCALL_DEFINE5(perf_counter_open, list_add_tail(&counter->owner_entry, ¤t->perf_counter_list); mutex_unlock(¤t->perf_counter_mutex); - counter->ns = get_pid_ns(current->nsproxy->pid_ns); - counter->id = atomic64_inc_return(&perf_counter_id); - fput_light(counter_file, fput_needed2); out_fput: -- 2.7.4