[RFC 01/18] capabilities: track actually used capabilities

[Topi Miettinen <toiwoton@gmail.com>]

Track what capabilities are actually used and present the current
situation in /proc/self/status.

Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
---
 fs/exec.c             | 1 +
 fs/proc/array.c       | 1 +
 include/linux/sched.h | 1 +
 kernel/capability.c   | 1 +
 4 files changed, 4 insertions(+)

diff --git a/fs/exec.c b/fs/exec.c
index 887c1c9..ff6f644 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1269,6 +1269,7 @@ void setup_new_exec(struct linux_binprm * bprm)
 		if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
 			set_dumpable(current->mm, suid_dumpable);
 	}
+	cap_clear(current->cap_used);
 
 	/* An exec changes our domain. We are no longer part of the thread
 	   group */
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 88c7de1..cccc9ee 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -343,6 +343,7 @@ static inline void task_cap(struct seq_file *m, struct task_struct *p)
 	render_cap_t(m, "CapEff:\t", &cap_effective);
 	render_cap_t(m, "CapBnd:\t", &cap_bset);
 	render_cap_t(m, "CapAmb:\t", &cap_ambient);
+	render_cap_t(m, "CapUsd:\t", &p->cap_used);
 }
 
 static inline void task_seccomp(struct seq_file *m, struct task_struct *p)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6e42ada..9c48a08 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1918,6 +1918,7 @@ struct task_struct {
 #ifdef CONFIG_MMU
 	struct task_struct *oom_reaper_list;
 #endif
+	kernel_cap_t	cap_used;	/* Capabilities actually used */
 /* CPU-specific state of this task */
 	struct thread_struct thread;
 /*
diff --git a/kernel/capability.c b/kernel/capability.c
index 45432b5..aad8854 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -380,6 +380,7 @@ bool ns_capable(struct user_namespace *ns, int cap)
 	}
 
 	if (security_capable(current_cred(), ns, cap) == 0) {
+		cap_raise(current->cap_used, cap);
 		current->flags |= PF_SUPERPRIV;
 		return true;
 	}
-- 
2.8.1