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 <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>
Cc: gregkh@suse.de
Cc: stable@kernel.org
LKML-Reference: <20110118161032.GC693@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 4 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index a962b1962eee..67d9bd70b746 100644
--- 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)