On Fri, Jul 24, 2015 at 6:04 AM, Lukasz Pawelczyk
<l.pawelczyk@xxxxxxxxxxx> wrote:
> This commit adds a new proc attribute, label_map that is required by an
> upcoming Smack namespace. In general it can be used to hold a map of
> labels, e.g. to be used in namespaces.
>
> Due to the nature of this file, the standard getprocattr hook might not
> be enough to handle it. The map's output can in principle be greater
> than page size to which the aforementioned hook is limited.
> To handle this properly a getprocattr_seq LSM hook has been added that
> makes it possible to handle any chosen proc attr by seq operations.
>
> See the documentation in the patch below for the details about how to
> use the hook.
>
> Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@xxxxxxxxxxx>
> ---
> fs/proc/base.c | 81 +++++++++++++++++++++++++++++++++++++++++++----
> include/linux/lsm_hooks.h | 15 +++++++++
> include/linux/security.h | 9 ++++++
> security/security.c | 8 +++++
> 4 files changed, 107 insertions(+), 6 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index aa50d1a..e5ac827 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -2338,20 +2338,77 @@ out:
> }
>
> #ifdef CONFIG_SECURITY
> +static int proc_pid_attr_open(struct inode *inode, struct file *file)
> +{
> + const char *name = file->f_path.dentry->d_name.name;
> + const struct seq_operations *ops;
> + struct task_struct *task;
> + struct seq_file *seq;
> + int ret;
> +
> + file->private_data = NULL;
> +
> + task = get_proc_task(inode);
> + if (!task)
> + return -ESRCH;
> +
> + /* don't use seq_ops if they are not provided by LSM */
> + ret = security_getprocattr_seq(task, name, &ops);
> + if (ret == -EOPNOTSUPP) {
> + put_task_struct(task);
> + return 0;
> + }
> + if (ret) {
> + put_task_struct(task);
> + return ret;
> + }
> +
> + ret = seq_open(file, ops);
> + if (ret) {
> + put_task_struct(task);
> + return ret;
> + }
> +
> + seq = file->private_data;
> + seq->private = task;
> +
> + return 0;
> +}
If you end up having to respin this patchset, you might consider
moving the "put_task_struct(...); return X;" code into a block at the
end of the function to simplify things a bit, for example:
static int proc_pid_attr_open(struct inode *inode, struct file *file)
{
const char *name = file->f_path.dentry->d_name.name;
const struct seq_operations *ops;
struct task_struct *task;
struct seq_file *seq;
int ret;
file->private_data = NULL;
task = get_proc_task(inode);
if (!task)
return -ESRCH;
/* don't use seq_ops if they are not provided by LSM */
ret = security_getprocattr_seq(task, name, &ops);
if (ret == -EOPNOTSUPP) {
ret = 0;
goto put_task;
}
if (ret)
goto put_task;
ret = seq_open(file, ops);
if (ret)
goto put_task;
seq = file->private_data;
seq->private = task;
return 0;
put_task:
put_task_struct(task);
return ret;
}
--
paul moore
www.paul-moore.com
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