linux-kernel - [PATCH] proc: don't show nonexistent capabilities

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Date:	Wed,  3 Oct 2012 00:30:32 +0400
From:	Andrew Vagin <avagin@...nvz.org>
To:	linux-kernel@...r.kernel.org
Cc:	criu@...nvz.org, Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	linux-security-module@...r.kernel.org
Subject: [PATCH] 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.

Cc: Serge Hallyn <serge.hallyn@...onical.com>
Cc: Pavel Emelyanov <xemul@...allels.com>
Signed-off-by: Andrew Vagin <avagin@...nvz.org>
---
 include/linux/capability.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/include/linux/capability.h b/include/linux/capability.h
index d10b7ed..1642778 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -420,7 +420,8 @@ extern const kernel_cap_t __cap_init_eff_set;
 #else /* HAND-CODED capability initializers */
 
 # define CAP_EMPTY_SET    ((kernel_cap_t){{ 0, 0 }})
-# define CAP_FULL_SET     ((kernel_cap_t){{ ~0, ~0 }})
+# define CAP_FULL_SET     ((kernel_cap_t){{ ~0, \
+					CAP_TO_MASK(CAP_LAST_CAP + 1) - 1 } })
 # define CAP_FS_SET       ((kernel_cap_t){{ CAP_FS_MASK_B0 \
 				    | CAP_TO_MASK(CAP_LINUX_IMMUTABLE), \
 				    CAP_FS_MASK_B1 } })
-- 
1.7.1

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