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Date:   Sat, 24 Sep 2022 19:22:50 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Christian Brauner <brauner@kernel.org>
Cc:     linux-fsdevel@vger.kernel.org, Seth Forshee <sforshee@kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        Eric Van Hensbergen <ericvh@gmail.com>,
        Latchesar Ionkov <lucho@ionkov.net>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Christian Schoenebeck <linux_oss@crudebyte.com>,
        v9fs-developer@lists.sourceforge.net
Subject: Re: [PATCH 07/29] 9p: implement set acl method
Message-ID: <Yy9K+lTiVF5SiwO0@ZenIV>
References: <20220922151728.1557914-1-brauner@kernel.org>
 <20220922151728.1557914-8-brauner@kernel.org>
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On Thu, Sep 22, 2022 at 05:17:05PM +0200, Christian Brauner wrote:

> +int v9fs_iop_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
> +		     struct posix_acl *acl, int type)
> +{
> +	int retval;
> +	void *value = NULL;
> +	size_t size = 0;
> +	struct v9fs_session_info *v9ses;
> +	struct inode *inode = d_inode(dentry);
> +
> +	v9ses = v9fs_dentry2v9ses(dentry);
> +
> +	if (acl) {
> +		retval = posix_acl_valid(inode->i_sb->s_user_ns, acl);
> +		if (retval)
> +			goto err_out;
> +
> +		size = posix_acl_xattr_size(acl->a_count);
> +
> +		value = kzalloc(size, GFP_NOFS);
> +		if (!value) {
> +			retval = -ENOMEM;
> +			goto err_out;
> +		}
> +
> +		retval = posix_acl_to_xattr(&init_user_ns, acl, value, size);
> +		if (retval < 0)
> +			goto err_out;
> +	}
> +
> +	/*
> +	 * set the attribute on the remote. Without even looking at the
> +	 * xattr value. We leave it to the server to validate
> +	 */
> +	if ((v9ses->flags & V9FS_ACCESS_MASK) != V9FS_ACCESS_CLIENT) {
> +		retval = v9fs_xattr_set(dentry, posix_acl_xattr_name(type),
> +					value, size, 0);
> +		goto err_out;
> +	}

> +	if (S_ISLNK(inode->i_mode))
> +		return -EOPNOTSUPP;
> +	if (!inode_owner_or_capable(&init_user_ns, inode))
> +		return -EPERM;

Shouldn't that chunk have been in the very beginning?  As it is, you've
got a leak here...