linux-kernel - Re: [PATCH v2 04/11] uprobes: Change prepare_uretprobe() to use uprobe

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Date:	Tue, 7 Jul 2015 14:52:27 +0200
From:	Anton Arapov <arapov@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ananth Mavinakayanahalli <ananth@...ibm.com>,
	David Long <dave.long@...aro.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Jan Willeke <willeke@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Mark Wielaard <mjw@...hat.com>,
	Pratyush Anand <panand@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 04/11] uprobes: Change prepare_uretprobe() to use
 uprobe_warn()

On Tue, Jul 07, 2015 at 03:22:47AM +0200, Oleg Nesterov wrote:
> Turn the last pr_warn() in uprobes.c into uprobe_warn().
> 
> While at it:
> 
>    - s/kzalloc/kmalloc, we initialize every member of ri
> 
>    - remove the pointless comment above the obvious code
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Acked-by: Anton Arapov <arapov@...il.com>

> ---
>  kernel/events/uprobes.c |   10 +++-------
>  1 files changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index eabdc21..4c941fe 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1541,9 +1541,9 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
>  		return;
>  	}
>  
> -	ri = kzalloc(sizeof(struct return_instance), GFP_KERNEL);
> +	ri = kmalloc(sizeof(struct return_instance), GFP_KERNEL);
>  	if (!ri)
> -		goto fail;
> +		return;
>  
>  	trampoline_vaddr = get_trampoline_vaddr();
>  	orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs);
> @@ -1561,8 +1561,7 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
>  			 * This situation is not possible. Likely we have an
>  			 * attack from user-space.
>  			 */
> -			pr_warn("uprobe: unable to set uretprobe pid/tgid=%d/%d\n",
> -						current->pid, current->tgid);
> +			uprobe_warn(current, "handle tail call");
>  			goto fail;
>  		}
>  
> @@ -1576,13 +1575,10 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
>  	ri->chained = chained;
>  
>  	utask->depth++;
> -
> -	/* add instance to the stack */
>  	ri->next = utask->return_instances;
>  	utask->return_instances = ri;
>  
>  	return;
> -
>   fail:
>  	kfree(ri);
>  }
> -- 
> 1.5.5.1
> 
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