linux-kernel - Re: [PATCH] kretprobes: reject registration if a symbol offset is specified

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Message-Id: <20170214084103.GF29806@in.ibm.com>
Date:   Tue, 14 Feb 2017 14:11:03 +0530
From:   Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kretprobes: reject registration if a symbol offset is
 specified

On Tue, Feb 14, 2017 at 02:01:18PM +0530, Naveen N. Rao wrote:
> Users shouldn't be able to specify an offset with kretprobes, as we always
> want to probe at function entry. Otherwise, we won't be able to capture
> the proper return address resulting in the kretprobe never firing.
> 
> With samples/kprobes/kretprobe_example.c including an offset:
> 	my_kretprobe.kp.offset = 40;
> 
> Before this patch, the probe gets planted but never fires.
> 
> After this patch:
> 	$ sudo insmod samples/kprobes/kretprobe_example.ko
> 	[sudo] password for naveen: 
> 	insmod: ERROR: could not insert module samples/kprobes/kretprobe_example.ko: Operation not permitted
> 
> And dmesg:
> 	[48253.757629] register_kretprobe failed, returned -22
> 
> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

Acked-by: Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>