[PATCH] uprobes: Fix utask->depth accounting in handle_trampoline()

[PATCH] uprobes: Fix utask->depth accounting in handle_trampoline()

[Oleg Nesterov]

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@vger.kernel.org
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Mikhail Kulemin <Mikhail.Kulemin@ru.ibm.com>
Reported-by: Hemant Kumar Shaw <hkshaw@linux.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

Re: [PATCH] uprobes: Fix utask->depth accounting in handle_trampoline()

[Srikar Dronamraju]

* Oleg Nesterov <oleg@redhat.com> [2013-09-11 17:47:26]:

> 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@vger.kernel.org
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> Reported-by: Mikhail Kulemin <Mikhail.Kulemin@ru.ibm.com>
> Reported-by: Hemant Kumar Shaw <hkshaw@linux.vnet.ibm.com>

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

Mikhail Kulemin has verified that this fix works for him.

> ---
>  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
> 
> 

-- 
Thanks and Regards
Srikar Dronamraju

[tip:perf/urgent] uprobes: Fix utask-> depth accounting in handle_trampoline()

[tip-bot for Oleg Nesterov]

Commit-ID:  878b5a6efd38030c7a90895dc8346e8fb1e09b4c
Gitweb:     http://git.kernel.org/tip/878b5a6efd38030c7a90895dc8346e8fb1e09b4c
Author:     Oleg Nesterov <oleg@redhat.com>
AuthorDate: Wed, 11 Sep 2013 17:47:26 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 12 Sep 2013 08:00:55 +0200

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.

Reported-by: Mikhail Kulemin <Mikhail.Kulemin@ru.ibm.com>
Reported-by: Hemant Kumar Shaw <hkshaw@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Anton Arapov <anton@redhat.com>
Cc: masami.hiramatsu.pt@hitachi.com
Cc: srikar@linux.vnet.ibm.com
Cc: systemtap@sourceware.org
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20130911154726.GA8093@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/events/uprobes.c | 4 +---
 1 file changed, 1 insertion(+), 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);
 	}