linux-kernel - Re: [PATCH 01/14] VFS: Factor out part of vfs_setxattr so it can be called from the SELinux hook for inode

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Message-ID: <20080930195108.GA21039@us.ibm.com>
Date:	Tue, 30 Sep 2008 14:51:08 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	"David P. Quigley" <dpquigl@...ho.nsa.gov>
Cc:	hch@...radead.org, viro@...iv.linux.org.uk, casey@...aufler-ca.com,
	sds@...ho.nsa.gov, matthew.dodd@...rta.com,
	trond.myklebust@....uio.no, bfields@...ldses.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov,
	labeled-nfs@...ux-nfs.org
Subject: Re: [PATCH 01/14] VFS: Factor out part of vfs_setxattr so it can
	be called from the SELinux hook for inode_setsecctx.

Quoting David P. Quigley (dpquigl@...ho.nsa.gov):
> This factors out the part of the vfs_setxattr function that performs the
> setting of the xattr and its notification. This is needed so the SELinux
> implementation of inode_setsecctx can handle the setting of it's xattr while
> maintaining the proper separation of layers.
> 
> Signed-off-by: Matthew N. Dodd <Matthew.Dodd@...rta.com>
> Signed-off-by: David P. Quigley <dpquigl@...ho.nsa.gov>

This part surely looks reasonable.

Acked-by: Serge Hallyn <serue@...ibm.com>
> ---
>  fs/xattr.c            |   55 +++++++++++++++++++++++++++++++++++++-----------
>  include/linux/xattr.h |    1 +
>  2 files changed, 43 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 468377e..2f93006 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -66,22 +66,28 @@ xattr_permission(struct inode *inode, const char *name, int mask)
>  	return inode_permission(inode, mask);
>  }
> 
> -int
> -vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
> -		size_t size, int flags)
> +/**
> + *  __vfs_setxattr_noperm - perform setxattr operation without performing
> + *  permission checks.
> + *
> + *  @dentry - object to perform setxattr on
> + *  @name - xattr name to set
> + *  @value - value to set @name to
> + *  @size - size of @value
> + *  @flags - flags to pass into filesystem operations
> + *
> + *  returns the result of the internal setxattr or setsecurity operations.
> + *
> + *  This function requires the caller to lock the inode's i_mutex before it
> + *  is executed. It also assumes that the caller will make the appropriate
> + *  permission checks.
> + */
> +int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
> +		const void *value, size_t size, int flags)
>  {
>  	struct inode *inode = dentry->d_inode;
> -	int error;
> -
> -	error = xattr_permission(inode, name, MAY_WRITE);
> -	if (error)
> -		return error;
> +	int error = -EOPNOTSUPP;
> 
> -	mutex_lock(&inode->i_mutex);
> -	error = security_inode_setxattr(dentry, name, value, size, flags);
> -	if (error)
> -		goto out;
> -	error = -EOPNOTSUPP;
>  	if (inode->i_op->setxattr) {
>  		error = inode->i_op->setxattr(dentry, name, value, size, flags);
>  		if (!error) {
> @@ -97,6 +103,29 @@ vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
>  		if (!error)
>  			fsnotify_xattr(dentry);
>  	}
> +
> +	return error;
> +}
> +
> +
> +int
> +vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
> +		size_t size, int flags)
> +{
> +	struct inode *inode = dentry->d_inode;
> +	int error;
> +
> +	error = xattr_permission(inode, name, MAY_WRITE);
> +	if (error)
> +		return error;
> +
> +	mutex_lock(&inode->i_mutex);
> +	error = security_inode_setxattr(dentry, name, value, size, flags);
> +	if (error)
> +		goto out;
> +
> +	error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
> +
>  out:
>  	mutex_unlock(&inode->i_mutex);
>  	return error;
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index d131e35..5c84af8 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -49,6 +49,7 @@ struct xattr_handler {
>  ssize_t xattr_getsecurity(struct inode *, const char *, void *, size_t);
>  ssize_t vfs_getxattr(struct dentry *, const char *, void *, size_t);
>  ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
> +int __vfs_setxattr_noperm(struct dentry *, const char *, const void *, size_t, int);
>  int vfs_setxattr(struct dentry *, const char *, const void *, size_t, int);
>  int vfs_removexattr(struct dentry *, const char *);
> 
> -- 
> 1.5.5.1
> 
> --
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