linux-kernel - [PATCH] uprobes: Fix utask->depth accounting in handle

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Message-ID: <20130911154726.GA8093@redhat.com>
Date:	Wed, 11 Sep 2013 17:47:26 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	anton@...hat.com, Hemant Kumar Shaw <hkshaw@...ux.vnet.ibm.com>,
	masami.hiramatsu.pt@...achi.com,
	Mikhail Kulemin <Mikhail.Kulemin@...ibm.com>,
	srikar@...ux.vnet.ibm.com, systemtap@...rceware.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] uprobes: Fix utask->depth accounting in handle_trampoline()

Currently utask->depth is simply the number of allocated/pending
return_instance's in uprobe_task->return_instances list.

handle_trampoline() should decrement this counter every time we
handle/free an instance, but due to typo it does this only if
->chained == T. This means that in the likely case this counter
is never decremented and the probed task can't report more than
MAX_URETPROBE_DEPTH events.

Cc: stable@...r.kernel.org
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Reported-by: Mikhail Kulemin <Mikhail.Kulemin@...ibm.com>
Reported-by: Hemant Kumar Shaw <hkshaw@...ux.vnet.ibm.com>
---
 kernel/events/uprobes.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index f356974..ad8e1bd 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1682,12 +1682,10 @@ static bool handle_trampoline(struct pt_regs *regs)
 		tmp = ri;
 		ri = ri->next;
 		kfree(tmp);
+		utask->depth--;
 
 		if (!chained)
 			break;
-
-		utask->depth--;
-
 		BUG_ON(!ri);
 	}
 
-- 
1.5.5.1


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