linux-kernel - [patch 23/86] kprobes: fix a memory leak in function pre_handler

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Date:	Fri, 10 Feb 2012 14:29:42 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Jiang Liu <jiang.liu@...wei.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [patch 23/86] kprobes: fix a memory leak in function pre_handler_kretprobe()

3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Jiang Liu <liuj97@...il.com>

commit 55ca6140e9bb307efc97a9301a4f501de02a6fd6 upstream.

In function pre_handler_kretprobe(), the allocated kretprobe_instance
object will get leaked if the entry_handler callback returns non-zero.
This may cause all the preallocated kretprobe_instance objects exhausted.

This issue can be reproduced by changing
samples/kprobes/kretprobe_example.c to probe "mutex_unlock".  And the fix
is straightforward: just put the allocated kretprobe_instance object back
onto the free_instances list.

[akpm@...ux-foundation.org: use raw_spin_lock/unlock]
Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
Acked-by: Jim Keniston <jkenisto@...ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
Cc: "David S. Miller" <davem@...emloft.net>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/kprobes.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1673,8 +1673,12 @@ static int __kprobes pre_handler_kretpro
 		ri->rp = rp;
 		ri->task = current;

-		if (rp->entry_handler && rp->entry_handler(ri, regs))
+		if (rp->entry_handler && rp->entry_handler(ri, regs)) {
+			raw_spin_lock_irqsave(&rp->lock, flags);
+			hlist_add_head(&ri->hlist, &rp->free_instances);
+			raw_spin_unlock_irqrestore(&rp->lock, flags);
 			return 0;
+		}

 		arch_prepare_kretprobe(ri, regs);

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