Christian Brauner <christian.brauner@xxxxxxxxxx> writes:
> Add a simple capability helper which makes it possible to determine
> whether a set of creds is ns capable wrt to the passed in credentials.
> This is not something exciting it's just a more pleasant wrapper around
> security_capable() by allowing ns_capable_common() to ake a const struct
> cred argument. In ptrace_has_cap() for example, we're using
> security_capable() directly. ns_capable_cred() will be used in the next
> patch to check against the target credentials the caller is going to
> switch to.
Given that this is to suppot setns. I don't understand the
justification for this.
Is it your intention to use the reduced permissions that you get
when you install a user namespace?
Why do you want to use the reduced permissions when installing multiple
namespaces at once?
Eric
> Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> Cc: Serge Hallyn <serge@xxxxxxxxxx>
> Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
> ---
> /* v2 */
> patch introduced
> ---
> include/linux/capability.h | 3 +++
> kernel/capability.c | 17 +++++++++++------
> 2 files changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/capability.h b/include/linux/capability.h
> index ecce0f43c73a..743a08d936fb 100644
> --- a/include/linux/capability.h
> +++ b/include/linux/capability.h
> @@ -40,6 +40,7 @@ struct cpu_vfs_cap_data {
> struct file;
> struct inode;
> struct dentry;
> +struct cred;
> struct task_struct;
> struct user_namespace;
>
> @@ -209,6 +210,8 @@ extern bool has_ns_capability_noaudit(struct task_struct *t,
> struct user_namespace *ns, int cap);
> extern bool capable(int cap);
> extern bool ns_capable(struct user_namespace *ns, int cap);
> +extern bool ns_capable_cred(const struct cred *cred,
> + struct user_namespace *ns, int cap);
> extern bool ns_capable_noaudit(struct user_namespace *ns, int cap);
> extern bool ns_capable_setid(struct user_namespace *ns, int cap);
> #else
> diff --git a/kernel/capability.c b/kernel/capability.c
> index 1444f3954d75..84425781917e 100644
> --- a/kernel/capability.c
> +++ b/kernel/capability.c
> @@ -361,8 +361,8 @@ bool has_capability_noaudit(struct task_struct *t, int cap)
> return has_ns_capability_noaudit(t, &init_user_ns, cap);
> }
>
> -static bool ns_capable_common(struct user_namespace *ns,
> - int cap,
> +static bool ns_capable_common(const struct cred *cred,
> + struct user_namespace *ns, int cap,
> unsigned int opts)
> {
> int capable;
> @@ -372,7 +372,7 @@ static bool ns_capable_common(struct user_namespace *ns,
> BUG();
> }
>
> - capable = security_capable(current_cred(), ns, cap, opts);
> + capable = security_capable(cred, ns, cap, opts);
> if (capable == 0) {
> current->flags |= PF_SUPERPRIV;
> return true;
> @@ -393,10 +393,15 @@ static bool ns_capable_common(struct user_namespace *ns,
> */
> bool ns_capable(struct user_namespace *ns, int cap)
> {
> - return ns_capable_common(ns, cap, CAP_OPT_NONE);
> + return ns_capable_common(current_cred(), ns, cap, CAP_OPT_NONE);
> }
> EXPORT_SYMBOL(ns_capable);
>
> +bool ns_capable_cred(const struct cred *cred, struct user_namespace *ns, int cap)
> +{
> + return ns_capable_common(cred, ns, cap, CAP_OPT_NONE);
> +}
> +
> /**
> * ns_capable_noaudit - Determine if the current task has a superior capability
> * (unaudited) in effect
> @@ -411,7 +416,7 @@ EXPORT_SYMBOL(ns_capable);
> */
> bool ns_capable_noaudit(struct user_namespace *ns, int cap)
> {
> - return ns_capable_common(ns, cap, CAP_OPT_NOAUDIT);
> + return ns_capable_common(current_cred(), ns, cap, CAP_OPT_NOAUDIT);
> }
> EXPORT_SYMBOL(ns_capable_noaudit);
>
> @@ -430,7 +435,7 @@ EXPORT_SYMBOL(ns_capable_noaudit);
> */
> bool ns_capable_setid(struct user_namespace *ns, int cap)
> {
> - return ns_capable_common(ns, cap, CAP_OPT_INSETID);
> + return ns_capable_common(current_cred(), ns, cap, CAP_OPT_INSETID);
> }
> EXPORT_SYMBOL(ns_capable_setid);
>
>
> base-commit: ae83d0b416db002fe95601e7f97f64b59514d936
