2009-10-30 13:53:13

by Ananth N Mavinakayanahalli

Subject: [PATCH] kprobes: Sanitize struct kretprobe_instance allocations

From: Ananth N Mavinakayanahalli <[email protected]>

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 <[email protected]>
---
kernel/kprobes.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6.32-rc5/kernel/kprobes.c
===================================================================
--- linux-2.6.32-rc5.orig/kernel/kprobes.c
+++ linux-2.6.32-rc5/kernel/kprobes.c
@@ -1014,9 +1014,9 @@ int __kprobes register_kretprobe(struct
/* 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);

2009-10-30 19:55:56

by Masami Hiramatsu

Subject: Re: [PATCH] kprobes: Sanitize struct kretprobe_instance allocations

Ananth N Mavinakayanahalli wrote:
> From: Ananth N Mavinakayanahalli<[email protected]>
>
> 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<[email protected]>

Acked-by: Masami Hiramatsu <[email protected]>

Thanks!

> ---
> kernel/kprobes.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> Index: linux-2.6.32-rc5/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.32-rc5.orig/kernel/kprobes.c
> +++ linux-2.6.32-rc5/kernel/kprobes.c
> @@ -1014,9 +1014,9 @@ int __kprobes register_kretprobe(struct
> /* 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);

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: [email protected]

2009-11-02 16:20:45

by Ananth N Mavinakayanahalli

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

Commit-ID: 4dae560f97fa438f373b53e14b30149c9e44a600
Gitweb: http://git.kernel.org/tip/4dae560f97fa438f373b53e14b30149c9e44a600
Author: Ananth N Mavinakayanahalli <[email protected]>
AuthorDate: Fri, 30 Oct 2009 19:23:10 +0530
Committer: Ingo Molnar <[email protected]>
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 <[email protected]>
Acked-by: Masami Hiramatsu <[email protected]>
Cc: Jim Keniston <[email protected]>
Cc: [email protected]
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
---
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);