linux-kernel - [PATCH 2.4] CAP_FS_MASK: add CAP_LINUX_IMMUTABLE and CAP

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Message-ID: <20090325173954.GA19299@us.ibm.com>
Date:	Wed, 25 Mar 2009 12:39:54 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Willy Tarreau <w@....eu>
Cc:	mtk.manpages@...il.com, Stephen Smalley <sds@...ch.ncsc.mil>,
	Andrew Morgan <morgan@...nel.org>,
	linux-security-module@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>, linux-nfs@...r.kernel.org,
	Igor Zhbanov <izh1979@...il.com>, stable@...nel.org,
	linux-api@...r.kernel.org, Chris Wright <chrisw@...s-sol.org>
Subject: [PATCH 2.4] CAP_FS_MASK: add CAP_LINUX_IMMUTABLE and CAP_MKNOD

When POSIX capabilities were introduced during the 2.1 Linux
cycle, the fs mask, which represents the capabilities which having
fsuid==0 is supposed to grant, did not include CAP_MKNOD and
CAP_LINUX_IMMUTABLE.  However, before capabilities the privilege
to call these did in fact depend upon fsuid==0.

This patch introduces those capabilities into the fsmask,
restoring the old behavior.

See the thread starting at http://lkml.org/lkml/2009/3/11/157 for
reference.

Reported-by: Igor Zhbanov <izh1979@...il.com>
Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
Cc: stable@...nel.org
---
 include/linux/capability.h |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff -Nrup linux-2.4.37/include/linux/capability.h linux-2.4.37.new/include/linux/capability.h
--- linux-2.4.37/include/linux/capability.h	2008-12-02 02:01:34.000000000 -0600
+++ linux-2.4.37.new/include/linux/capability.h	2009-03-25 11:09:47.000000000 -0500
@@ -99,10 +99,6 @@ typedef __u32 kernel_cap_t;
 
 #define CAP_FSETID           4
 
-/* Used to decide between falling back on the old suser() or fsuser(). */
-
-#define CAP_FS_MASK          0x1f
-
 /* Overrides the restriction that the real or effective user ID of a
    process sending a signal must match the real or effective user ID
    of the process receiving the signal. */
@@ -301,6 +297,16 @@ extern kernel_cap_t cap_bset;
 
 #endif
 
+/* Used to decide between falling back on the old suser() or fsuser(). */
+
+#define CAP_FS_MASK	(CAP_TO_MASK(CAP_CHOWN)			\
+			| CAP_TO_MASK(CAP_DAC_OVERRIDE)		\
+			| CAP_TO_MASK(CAP_DAC_READ_SEARCH)	\
+			| CAP_TO_MASK(CAP_FOWNER)		\
+			| CAP_TO_MASK(CAP_FSETID)		\
+			| CAP_TO_MASK(CAP_LINUX_IMMUTABLE)	\
+			| CAP_TO_MASK(CAP_MKNOD))
+
 #define CAP_EMPTY_SET       to_cap_t(0)
 #define CAP_FULL_SET        to_cap_t(~0)
 #define CAP_INIT_EFF_SET    to_cap_t(~0 & ~CAP_TO_MASK(CAP_SETPCAP))
--
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