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Subject: Re: [PATCH] nfsd: Return EPERM on utime/utimes/lutimes calls instead
 of EACCESS in some cases
To:     "J. Bruce Fields" <bfields@fieldses.org>
CC:     <jlayton@kernel.org>, <linux-nfs@vger.kernel.org>,
        <houtao1@huawei.com>, <zhaohongjiang@huawei.com>
References: <1543564290-147370-1-git-send-email-zhengbin13@huawei.com>
 <4e0152c4-bbe9-4246-27ee-bae2fee9129d@huawei.com>
 <20181204201357.GC3903@fieldses.org>
 <e3073b92-1eab-78f5-09ae-629e6496fac4@huawei.com>
 <20181205013717.GA6093@fieldses.org>
From:   "zhengbin (A)" <zhengbin13@huawei.com>
Message-ID: <bfa4c769-79dd-79fe-c29f-75507719aec0@huawei.com>
Date:   Wed, 5 Dec 2018 09:43:06 +0800
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 second parameter of utime/utimes/lutimes is not NULL   -------> maybe lutimes should be removed? I think "second parameter of utime/utimes is not NULL" would be better

On 2018/12/5 9:37, J. Bruce Fields wrote:
> On Wed, Dec 05, 2018 at 09:04:22AM +0800, zhengbin (A) wrote:
>> thanks,
>>>>> As the man(3) page for utime/utimes/lutimes, EPERM is returned
>>
>> -------->this should be As the man page for utime/utimes/lutimes, my little mistake. utime/utimes are man(2), lutimes is man(3)
>>
>> I send v2 patch?Or when you apply, help modify it?
> 
> Does this look OK?
> 
> --b.
> 
> commit eb6d67589750
> Author: zhengbin <zhengbin13@huawei.com>
> Date:   Fri Nov 30 16:04:25 2018 +0800
> 
>     nfsd: Return EPERM, not EACCES, in some SETATTR cases
>     
>     As the man(2) page for utime/utimes states, EPERM is returned when the
>     second parameter of utime/utimes/lutimes is not NULL, the caller's
>     effective UID does not match the owner of the file, and the caller is
>     not privileged.
>     
>     However, in a NFS directory mounted from knfsd, it will return EACCES
>     (from nfsd_setattr-> fh_verify->nfsd_permission).  This patch fixes
>     that.
>     
>     Signed-off-by: zhengbin <zhengbin13@huawei.com>
>     Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index eb67098117b4..9824e32b2f23 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -396,10 +396,23 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
>  	bool		get_write_count;
>  	bool		size_change = (iap->ia_valid & ATTR_SIZE);
>  
> -	if (iap->ia_valid & (ATTR_ATIME | ATTR_MTIME | ATTR_SIZE))
> +	if (iap->ia_valid & ATTR_SIZE) {
>  		accmode |= NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE;
> -	if (iap->ia_valid & ATTR_SIZE)
>  		ftype = S_IFREG;
> +	}
> +
> +	/*
> +	 * If utimes(2) and friends are called with times not NULL, we should
> +	 * not set NFSD_MAY_WRITE bit. Otherwise fh_verify->nfsd_permission
> +	 * will return EACCESS, when the caller's effective UID does not match
> +	 * the owner of the file, and the caller is not privileged. In this
> +	 * situation, we should return EPERM(notify_change will return this).
> +	 */
> +	if (iap->ia_valid & (ATTR_ATIME | ATTR_MTIME)) {
> +		accmode |= NFSD_MAY_OWNER_OVERRIDE;
> +		if (!(iap->ia_valid & (ATTR_ATIME_SET | ATTR_MTIME_SET)))
> +			accmode |= NFSD_MAY_WRITE;
> +	}
>  
>  	/* Callers that do fh_verify should do the fh_want_write: */
>  	get_write_count = !fhp->fh_dentry;
> 
> .
>