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Subject[206/272] perf: Validate cpu early in perf_event_alloc()
2.6.37-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Oleg Nesterov <oleg@redhat.com>

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>

---
kernel/perf_event.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2105,9 +2105,6 @@ find_get_context(struct pmu *pmu, struct
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
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

if (!overflow_handler && parent_event)
overflow_handler = parent_event->overflow_handler;
-
+
event->overflow_handler = overflow_handler;

if (attr->disabled)



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