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Date: Wed, 20 Apr 2011 03:18:20 +0100
Message-ID: <BANLkTinXVDrLnMOo17pqua5+38yQsezG6g@mail.gmail.com>
Subject: Re: [PATCH] tmpfs: implement generic xattr support
From: Phillip Lougher <phillip.lougher@gmail.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Michal Suchanek <hramrach@centrum.cz>, Andreas Dilger <adilger@dilger.ca>,
        Jiri Kosina <jkosina@suse.cz>, Ric Wheeler <ricwheeler@gmail.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        David Howells <dhowells@redhat.com>, Ian Kent <ikent@redhat.com>,
        Jeff Moyer <jmoyer@redhat.com>, Christoph Hellwig <hch@infradead.org>,
        Hugh Dickins <hughd@google.com>, Eric Paris <eparis@redhat.com>
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On Tue, Apr 19, 2011 at 9:04 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:

> +static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)

> + ? ? ? spin_lock(&dentry->d_inode->i_lock);
> + ? ? ? list_for_each_entry(xattr, &info->xattr_list, list) {
> + ? ? ? ? ? ? ? /* skip "trusted." attributes for unprivileged callers */
> + ? ? ? ? ? ? ? if (!trusted && xattr_is_trusted(xattr->name))
> + ? ? ? ? ? ? ? ? ? ? ? continue;
> +
> + ? ? ? ? ? ? ? used += strlen(xattr->name) + 1;
> + ? ? ? ? ? ? ? if (buffer) {
> + ? ? ? ? ? ? ? ? ? ? ? if (size < used) {
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? used = -ERANGE;
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? break;
> + ? ? ? ? ? ? ? ? ? ? ? }
> + ? ? ? ? ? ? ? ? ? ? ? strncpy(buffer, xattr->name, strlen(xattr->name) + 1);
>+                        buffer += strlen(xattr->name) + 1;

Why are you doing a strncpy here?  strcpy() isn't going to copy more
than strlen(xattr->name) + 1 bytes, and you know buffer is large
enough to hold that because of the previous if (size < used) check?

If you assigned the first strlen(xattr->name) + 1 to a temporary
variable, you could use memcpy here, and avoid the 3 repeated
strlen(xattr->name) calls.

Phillip
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