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Date: Mon, 27 Feb 2012 14:46:02 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Hugh Dickins <hughd@google.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@intel.com>,
        James Morris <jmorris@namei.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org
Subject: Re: [PATCH] tmpfs: security xattr setting on inode creation
Message-Id: <20120227144602.07f5ec33.akpm@linux-foundation.org>
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On Fri, 24 Feb 2012 19:19:22 -0800 (PST)
Hugh Dickins <hughd@google.com> wrote:

> +/*
> + * Callback for security_inode_init_security() for acquiring xattrs.
> + */
> +static int shmem_initxattrs(struct inode *inode,
> +			    const struct xattr *xattr_array,
> +			    void *fs_info)
> +{
> +	struct shmem_inode_info *info = SHMEM_I(inode);
> +	const struct xattr *xattr;
> +	struct shmem_xattr *new_xattr;
> +	size_t len;
> +
> +	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
> +		new_xattr = shmem_xattr_alloc(xattr->value, xattr->value_len);
> +		if (!new_xattr)
> +			return -ENOMEM;
> +
> +		len = strlen(xattr->name) + 1;
> +		new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
> +					  GFP_KERNEL);
> +		if (!new_xattr->name) {
> +			kfree(new_xattr);
> +			return -ENOMEM;
> +		}
> +
> +		memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
> +		       XATTR_SECURITY_PREFIX_LEN);
> +		memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
> +		       xattr->name, len);
> +
> +		spin_lock(&info->lock);
> +		list_add(&new_xattr->list, &info->xattr_list);
> +		spin_unlock(&info->lock);
> +	}
> +
> +	return 0;
> +}

So if there's a kmalloc failure partway through the array, we leave a
partially xattrified inode in place.

Are we sure this is OK?