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SubjectRe: [PATCH 14/25] sysfs: Don't use lookup_one_len_kern
On Tue, Aug 07, 2007 at 03:23:57PM -0600, Eric W. Biederman wrote:
>
> Upon inspection it appears that there is no looking of the
> inode mutex in lookup_one_len_kern and we aren't calling
> it with the inode mutex and that is wrong.
>
> So this patch rolls our own dcache insertion function that
> does exactly what we need it to do. As it turns out this
> is pretty trivial to do and it makes the code easier to
> audit.
>
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> ---
> fs/sysfs/dir.c | 41 +++++++++++++++++++++++++++++++++++++++--
> 1 files changed, 39 insertions(+), 2 deletions(-)
>
> diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
> index a9bdb12..1d53c2a 100644
> --- a/fs/sysfs/dir.c
> +++ b/fs/sysfs/dir.c
> @@ -765,6 +765,44 @@ static struct dentry *__sysfs_get_dentry(struct super_block *sb, struct sysfs_di
> return dentry;
> }
>
> +static struct dentry *sysfs_add_dentry(struct dentry *parent, struct sysfs_dirent *sd)
> +{
> + struct qstr name;
> + struct dentry *dentry;
> + struct inode *inode;
> +
> + mutex_lock(&parent->d_inode->i_mutex);
> + mutex_lock(&sysfs_mutex);
> + dentry = ERR_PTR(-EINVAL);
> + if (parent->d_fsdata != sd->s_parent)
> + goto out;
> +
> + name.name = sd->s_name;
> + name.len = strlen(sd->s_name);
> + dentry = d_hash_and_lookup(parent, &name);
> + if (dentry)
> + goto out;
> +
> + dentry = d_alloc(parent, &name);
> + if (!dentry) {
> + dentry = ERR_PTR(-ENOMEM);
> + goto out;
> + }
> +
> + inode = sysfs_get_inode(sd);
> + if (!inode) {
> + dput(dentry);
> + dentry = ERR_PTR(-ENOMEM);
> + goto out;
> + }
> + d_instantiate(dentry, inode);
> + sysfs_attach_dentry(sd, dentry);
> +out:
> + mutex_unlock(&sysfs_mutex);
> + mutex_unlock(&parent->d_inode->i_mutex);
> + return dentry;
> +}

This is virtually identical to

mutex_lock(&parent_dentry->d_inode->i_mutex);
dentry = lookup_one_len_kern(cur->s_name, parent_dentry,
strlen(cur->s_name));
mutex_unlock(&parent_dentry->d_inode->i_mutex);

right? I don't think we need to duplicate the code here. Or is it
needed for later multi-sb thing?

--
tejun
-
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