[tip:tracing/core] kprobes: Sanitize struct kretprobe_instance allocations

[tip-bot for Ananth N Mavinakayanahalli <ananth@in.ibm.com>]

Commit-ID:  4dae560f97fa438f373b53e14b30149c9e44a600
Gitweb:     http://git.kernel.org/tip/4dae560f97fa438f373b53e14b30149c9e44a600
Author:     Ananth N Mavinakayanahalli <ananth@in.ibm.com>
AuthorDate: Fri, 30 Oct 2009 19:23:10 +0530
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 2 Nov 2009 17:00:18 +0100

kprobes: Sanitize struct kretprobe_instance allocations

For as long as kretprobes have existed, we've allocated NR_CPUS
instances of kretprobe_instance structures. With the default
value of CONFIG_NR_CPUS increasing on certain architectures, we
are potentially wasting kernel memory.

See http://sourceware.org/bugzilla/show_bug.cgi?id=10839#c3 for
more details.

Use a saner num_possible_cpus() instead of NR_CPUS for
allocation.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: fweisbec@gmail.com
LKML-Reference: <20091030135310.GA22230@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/kprobes.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 5240d75..1494e85 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1014,9 +1014,9 @@ int __kprobes register_kretprobe(struct kretprobe *rp)
 	/* Pre-allocate memory for max kretprobe instances */
 	if (rp->maxactive <= 0) {
 #ifdef CONFIG_PREEMPT
-		rp->maxactive = max(10, 2 * NR_CPUS);
+		rp->maxactive = max(10, 2 * num_possible_cpus());
 #else
-		rp->maxactive = NR_CPUS;
+		rp->maxactive = num_possible_cpus();
 #endif
 	}
 	spin_lock_init(&rp->lock);