Commit 7b9a7ec5 authored Dec 17, 2012 by Andrew Vagin Committed by Linus Torvalds Dec 17, 2012

proc: don't show nonexistent capabilities



Without this patch it is really hard to interpret a bounding set, if
CAP_LAST_CAP is unknown for a current kernel.

Non-existant capabilities can not be deleted from a bounding set with help
of prctl.

E.g.: Here are two examples without/with this patch.

  CapBnd:	ffffffe0fdecffff
  CapBnd:	00000000fdecffff

I suggest to hide non-existent capabilities. Here is two reasons.
* It's logically and easier for using.
* It helps to checkpoint-restore capabilities of tasks, because tasks
can be restored on another kernel, where CAP_LAST_CAP is bigger.

Signed-off-by: Andrew Vagin <avagin@openvz.org>
Cc: Andrew G. Morgan <morgan@kernel.org>
Reviewed-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 992fb6e1

fs/proc/array.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -308,6 +308,10 @@ static void render_cap_t(struct seq_file m, const char header,
		seq_putc(m, '\n');
		}

		/* Remove non-existent capabilities */
		#define NORM_CAPS(v) (v.cap[CAP_TO_INDEX(CAP_LAST_CAP)] &= \
		CAP_TO_MASK(CAP_LAST_CAP + 1) - 1)

		static inline void task_cap(struct seq_file m, struct task_struct p)
		{
		const struct cred *cred;
		@@ -321,6 +325,11 @@ static inline void task_cap(struct seq_file m, struct task_struct p)
		cap_bset = cred->cap_bset;
		rcu_read_unlock();

		NORM_CAPS(cap_inheritable);
		NORM_CAPS(cap_permitted);
		NORM_CAPS(cap_effective);
		NORM_CAPS(cap_bset);

		render_cap_t(m, "CapInh:\t", &cap_inheritable);
		render_cap_t(m, "CapPrm:\t", &cap_permitted);
		render_cap_t(m, "CapEff:\t", &cap_effective);