perf: Validate cpu early in perf_event_alloc()

Starting from perf_event_alloc()->perf_init_event(), the kernel
assumes that event->cpu is either -1 or the valid CPU number.

Change perf_event_alloc() to validate this argument early. This
also means we can remove the similar check in
find_get_context().

Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: Alan Stern <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Prasad <[email protected]>
Cc: Roland McGrath <[email protected]>
Cc: [email protected]
Cc: [email protected]
LKML-Reference: <20110118161032[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index a962b1962eee375b3e3e1e729442c31ae8c881da..67d9bd70b7460901a474d8585c80c13e274da818 100644 (file)
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2233,9 +2233,6 @@ find_get_context(struct pmu *pmu, struct task_struct *task, int cpu)
                if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
                        return ERR_PTR(-EACCES);
 
-               if (cpu < 0 || cpu >= nr_cpumask_bits)
-                       return ERR_PTR(-EINVAL);
-
                /*
                 * We could be clever and allow to attach a event to an
                 * offline CPU and activate it when the CPU comes up, but
@@ -5541,6 +5538,11 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
        struct hw_perf_event *hwc;
        long err;
 
+       if ((unsigned)cpu >= nr_cpu_ids) {
+               if (!task || cpu != -1)
+                       return ERR_PTR(-EINVAL);
+       }
+
        event = kzalloc(sizeof(*event), GFP_KERNEL);
        if (!event)
                return ERR_PTR(-ENOMEM);
@@ -5589,7 +5591,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 
        if (!overflow_handler && parent_event)
                overflow_handler = parent_event->overflow_handler;
-       
+
        event->overflow_handler = overflow_handler;
 
        if (attr->disabled)