linux-kernel - Re: [PATCH] staging/lustre/llite: Use memdup_user() rather than duplicating its implementation

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Message-ID: <66b32046-56ee-430e-e80e-1cdd5a8e68c4@wanadoo.fr>
Date:   Sun, 21 Aug 2016 11:59:23 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging/lustre/llite: Use memdup_user() rather than
 duplicating its implementation

Le 21/08/2016 à 11:45, SF Markus Elfring a écrit :
> From: Markus Elfring <elfring@...rs.sourceforge.net>
> Date: Sun, 21 Aug 2016 11:30:57 +0200
>
> Reuse existing functionality from memdup_user() instead of keeping
> duplicate source code.
>
> This issue was detected by using the Coccinelle software.
>
> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> ---
>   drivers/staging/lustre/lustre/llite/dir.c | 12 +++---------
>   1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/staging/lustre/lustre/llite/dir.c b/drivers/staging/lustre/lustre/llite/dir.c
> index 031c9e4..8b70e42 100644
> --- a/drivers/staging/lustre/lustre/llite/dir.c
> +++ b/drivers/staging/lustre/lustre/llite/dir.c
> @@ -1676,14 +1676,9 @@ out_poll:
>   	case LL_IOC_QUOTACTL: {
>   		struct if_quotactl *qctl;
>   
> -		qctl = kzalloc(sizeof(*qctl), GFP_NOFS);
Same as previously reported in another patch, GFP_NOFS has not the same 
meaning than GPF_KERNEL.
So your proposed clean-up is not 100% equivalent.

Are your sure that GPF_KERNEL instead of GFP_NOFS is right in this code?

Maybe, the coccinelle check should be tweak to only spot "kzalloc(..., 
GFP_KERNEL)" allocation?

> -		if (!qctl)
> -			return -ENOMEM;
> -
> -		if (copy_from_user(qctl, (void __user *)arg, sizeof(*qctl))) {
> -			rc = -EFAULT;
> -			goto out_quotactl;
> -		}
> +		qctl = memdup_user((void __user *)arg, sizeof(*qctl));
> +		if (IS_ERR(qctl))
> +			return PTR_ERR(qctl);
>   
>   		rc = quotactl_ioctl(sbi, qctl);
>   
> @@ -1691,7 +1686,6 @@ out_poll:
>   					    sizeof(*qctl)))
>   			rc = -EFAULT;
>   
> -out_quotactl:
>   		kfree(qctl);
>   		return rc;
>   	}



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