perf: Validate cpu early in perf_event_alloc()

commit 66832eb4baaaa9abe4c993ddf9113a79e39b9915 upstream.

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 <oleg@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
LKML-Reference: <20110118161032.GC693@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 31ce59108c9d8f434fb930b7d75fc97cd7b31cf9..64668bd5d81bfc86f93e366f80108cfbe998e0ef 100644 (file)
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2105,9 +2105,6 @@ 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
@@ -5304,6 +5301,11 @@ 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);
@@ -5352,7 +5354,7 @@ 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)