Re: [PATCH] nfsd: Return EPERM on utime/utimes/lutimes calls instead of EACCESS in some cases

["zhengbin (A)" <zhengbin13@huawei.com>]

hi, J. Bruce Fields, Jeff Layton

 When you have time, confirm it? thanks

On 2018/11/30 15:51, zhengbin wrote:
> As the man(3) page for utime/utimes/lutimes, 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, it will return EACCESS(nfsd_setattr->
> fh_verify->nfsd_permission), This patch fix this.
> 
> Signed-off-by: zhengbin <zhengbin13@huawei.com>
> ---
>  fs/nfsd/vfs.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index eb67098..9824e32 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;
> --
> 2.7.4
> 
> 
> .
>