On Fri, Jul 24, 2015 at 12:04:36PM +0200, Lukasz Pawelczyk 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>
Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
> ---
> 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;
> +}
> +
> +static int proc_pid_attr_release(struct inode *inode, struct file *file)
> +{
> + struct seq_file *seq;
> + struct task_struct *task;
> +
> + /* don't use seq_ops if they were not provided by LSM */
> + if (file->private_data == NULL)
> + return 0;
> +
> + seq = file->private_data;
> + task = seq->private;
> + put_task_struct(task);
> +
> + return seq_release(inode, file);
> +}
> +
> static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
> size_t count, loff_t *ppos)
> {
> - struct inode * inode = file_inode(file);
> + struct inode *inode = file_inode(file);
> + const char *name = file->f_path.dentry->d_name.name;
> char *p = NULL;
> ssize_t length;
> - struct task_struct *task = get_proc_task(inode);
> + struct task_struct *task;
> +
> + /* use seq_ops if they were provided by LSM */
> + if (file->private_data)
> + return seq_read(file, buf, count, ppos);
>
> + task = get_proc_task(inode);
> if (!task)
> return -ESRCH;
>
> - length = security_getprocattr(task,
> - (char*)file->f_path.dentry->d_name.name,
> - &p);
> + length = security_getprocattr(task, (char *)name, &p);
> put_task_struct(task);
> if (length > 0)
> length = simple_read_from_buffer(buf, count, ppos, p, length);
> @@ -2359,6 +2416,15 @@ static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
> return length;
> }
>
> +static loff_t proc_pid_attr_lseek(struct file *file, loff_t offset, int whence)
> +{
> + /* use seq_ops if they were provided by LSM */
> + if (file->private_data)
> + return seq_lseek(file, offset, whence);
> +
> + return generic_file_llseek(file, offset, whence);
> +}
> +
> static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
> size_t count, loff_t *ppos)
> {
> @@ -2405,9 +2471,11 @@ out_no_task:
> }
>
> static const struct file_operations proc_pid_attr_operations = {
> + .open = proc_pid_attr_open,
> + .release = proc_pid_attr_release,
> .read = proc_pid_attr_read,
> + .llseek = proc_pid_attr_lseek,
> .write = proc_pid_attr_write,
> - .llseek = generic_file_llseek,
> };
>
> static const struct pid_entry attr_dir_stuff[] = {
> @@ -2417,6 +2485,7 @@ static const struct pid_entry attr_dir_stuff[] = {
> REG("fscreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
> REG("keycreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
> REG("sockcreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
> + REG("label_map", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
> };
>
> static int proc_attr_dir_readdir(struct file *file, struct dir_context *ctx)
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 228558c..d347e66 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1208,6 +1208,18 @@
> * @name full extended attribute name to check against
> * LSM as a MAC label.
> *
> + * @getprocattr_seq:
> + * An alternative to the getprocattr, that makes it possible for an attr
> + * file to be handled by seq operations. If this function returns valid
> + * @ops for a specific @name, those operations will be used and
> + * getprocattr will not be called.
> + * A proper task for the file is then passed in seq_file->private.
> + * @p a task associated with the proc file.
> + * @name name of the attr file under /proc/$PID/attr/ to be handled.
> + * @ops (out) seq_operations to be used for @name.
> + * Return 0 if @name is to be handled by seq, EOPNOTSUPP if getprocattr()
> + * should be used. Other errors will be passed to user-space.
> + *
> * @secid_to_secctx:
> * Convert secid to security context. If secdata is NULL the length of
> * the result will be returned in seclen, but no secdata will be returned.
> @@ -1525,6 +1537,8 @@ union security_list_options {
>
> void (*d_instantiate)(struct dentry *dentry, struct inode *inode);
>
> + int (*getprocattr_seq)(struct task_struct *p, const char *name,
> + const struct seq_operations **ops);
> int (*getprocattr)(struct task_struct *p, char *name, char **value);
> int (*setprocattr)(struct task_struct *p, char *name, void *value,
> size_t size);
> @@ -1774,6 +1788,7 @@ struct security_hook_heads {
> struct list_head sem_semop;
> struct list_head netlink_send;
> struct list_head d_instantiate;
> + struct list_head getprocattr_seq;
> struct list_head getprocattr;
> struct list_head setprocattr;
> struct list_head ismaclabel;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 1b0eccc..3090bb2 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -345,6 +345,8 @@ int security_sem_semctl(struct sem_array *sma, int cmd);
> int security_sem_semop(struct sem_array *sma, struct sembuf *sops,
> unsigned nsops, int alter);
> void security_d_instantiate(struct dentry *dentry, struct inode *inode);
> +int security_getprocattr_seq(struct task_struct *p, const char *name,
> + const struct seq_operations **ops);
> int security_getprocattr(struct task_struct *p, char *name, char **value);
> int security_setprocattr(struct task_struct *p, char *name, void *value, size_t size);
> int security_netlink_send(struct sock *sk, struct sk_buff *skb);
> @@ -1057,6 +1059,13 @@ static inline int security_sem_semop(struct sem_array *sma,
> static inline void security_d_instantiate(struct dentry *dentry, struct inode *inode)
> { }
>
> +static inline int security_getprocattr_seq(struct task_struct *p,
> + const char *name,
> + const struct seq_operations **ops)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> static inline int security_getprocattr(struct task_struct *p, char *name, char **value)
> {
> return -EINVAL;
> diff --git a/security/security.c b/security/security.c
> index 5e66388..e348e38 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1126,6 +1126,12 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
> }
> EXPORT_SYMBOL(security_d_instantiate);
>
> +int security_getprocattr_seq(struct task_struct *p, const char *name,
> + const struct seq_operations **ops)
> +{
> + return call_int_hook(getprocattr_seq, -EOPNOTSUPP, p, name, ops);
> +}
> +
> int security_getprocattr(struct task_struct *p, char *name, char **value)
> {
> return call_int_hook(getprocattr, -EINVAL, p, name, value);
> @@ -1778,6 +1784,8 @@ struct security_hook_heads security_hook_heads = {
> .netlink_send = LIST_HEAD_INIT(security_hook_heads.netlink_send),
> .d_instantiate =
> LIST_HEAD_INIT(security_hook_heads.d_instantiate),
> + .getprocattr_seq =
> + LIST_HEAD_INIT(security_hook_heads.getprocattr_seq),
> .getprocattr = LIST_HEAD_INIT(security_hook_heads.getprocattr),
> .setprocattr = LIST_HEAD_INIT(security_hook_heads.setprocattr),
> .ismaclabel = LIST_HEAD_INIT(security_hook_heads.ismaclabel),
> --
> 2.4.3
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