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Date: Tue, 7 Jul 2015 14:51:23 +0200
From: Anton Arapov <arapov@gmail.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Ananth Mavinakayanahalli <ananth@in.ibm.com>,
        David Long <dave.long@linaro.org>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        "Frank Ch. Eigler" <fche@redhat.com>, Ingo Molnar <mingo@kernel.org>,
        Jan Willeke <willeke@de.ibm.com>, Jim Keniston <jkenisto@us.ibm.com>,
        Mark Wielaard <mjw@redhat.com>, Pratyush Anand <panand@redhat.com>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 03/11] uprobes: Send SIGILL if handle_trampoline()
 fails
Message-ID: <20150707125123.GC5946@troglodyte.intinfra.com>
References: <20150707012210.GA7466@redhat.com>
 <20150707012243.GA7500@redhat.com>
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On Tue, Jul 07, 2015 at 03:22:43AM +0200, Oleg Nesterov wrote:
> 1. It doesn't make sense to continue if handle_trampoline() fails,
>    change handle_swbp() to always return after this call.
> 
> 2. Turn pr_warn() into uprobe_warn(), and change handle_trampoline()
>    to send SIGILL on failure. It is pointless to return to user mode
>    with the corrupted instruction_pointer() which we can't restore.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Anton Arapov <arapov@gmail.com>


> ---
>  kernel/events/uprobes.c |   21 ++++++++++-----------
>  1 files changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index d8c702f..eabdc21 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1770,7 +1770,7 @@ handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
>  	up_read(&uprobe->register_rwsem);
>  }
>  
> -static bool handle_trampoline(struct pt_regs *regs)
> +static void handle_trampoline(struct pt_regs *regs)
>  {
>  	struct uprobe_task *utask;
>  	struct return_instance *ri;
> @@ -1778,11 +1778,11 @@ static bool handle_trampoline(struct pt_regs *regs)
>  
>  	utask = current->utask;
>  	if (!utask)
> -		return false;
> +		goto sigill;
>  
>  	ri = utask->return_instances;
>  	if (!ri)
> -		return false;
> +		goto sigill;
>  
>  	/*
>  	 * TODO: we should throw out return_instance's invalidated by
> @@ -1804,8 +1804,12 @@ static bool handle_trampoline(struct pt_regs *regs)
>  	}
>  
>  	utask->return_instances = ri;
> +	return;
> +
> + sigill:
> +	uprobe_warn(current, "handle uretprobe, sending SIGILL.");
> +	force_sig_info(SIGILL, SEND_SIG_FORCED, current);
>  
> -	return true;
>  }
>  
>  bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs)
> @@ -1824,13 +1828,8 @@ static void handle_swbp(struct pt_regs *regs)
>  	int uninitialized_var(is_swbp);
>  
>  	bp_vaddr = uprobe_get_swbp_addr(regs);
> -	if (bp_vaddr == get_trampoline_vaddr()) {
> -		if (handle_trampoline(regs))
> -			return;
> -
> -		pr_warn("uprobe: unable to handle uretprobe pid/tgid=%d/%d\n",
> -						current->pid, current->tgid);
> -	}
> +	if (bp_vaddr == get_trampoline_vaddr())
> +		return handle_trampoline(regs);
>  
>  	uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
>  	if (!uprobe) {
> -- 
> 1.5.5.1
>