linux-kernel - [PATCH v3] pci: use security_capable() when checking capablities during config space read

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Message-ID: <20110215012149.GM9869@sequoia.sous-sol.org>
Date:	Mon, 14 Feb 2011 17:21:49 -0800
From:	Chris Wright <chrisw@...s-sol.org>
To:	James Morris <jmorris@...ei.org>
Cc:	Chris Wright <chrisw@...s-sol.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Airlie <airlied@...il.com>,
	Dave Young <hidave.darkstar@...il.com>,
	linux-kernel@...r.kernel.org, David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, Alex Riesen <raa.lkml@...il.com>,
	Sedat Dilek <sedat.dilek@...glemail.com>,
	Eric Paris <eparis@...hat.com>
Subject: [PATCH v3] pci: use security_capable() when checking capablities
 during config space read

This reintroduces commit 47970b1b which was subsequently reverted
as f00eaeea.  The original change was broken and caused X startup
failures and generally made privileged processes incapable of reading
device dependent config space.  The normal capable() interface returns
true on success, but the LSM interface returns 0 on success.  This thinko
is now fixed in this patch, and has been confirmed to work properly.

So, once again...Eric Paris noted that commit de139a3 ("pci: check caps
from sysfs file open to read device dependent config space") caused the
capability check to bypass security modules and potentially auditing.
Rectify this by calling security_capable() when checking the open file's
capabilities for config space reads.

Reported-by: Eric Paris <eparis@...hat.com>
Tested-by: Dave Young <hidave.darkstar@...il.com>
Acked-by: James Morris <jmorris@...ei.org>
Cc: Dave Airlie <airlied@...il.com>
Cc: Alex Riesen <raa.lkml@...il.com>
Cc: Sedat Dilek <sedat.dilek@...glemail.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Chris Wright <chrisw@...s-sol.org>
---
v2: added Reported-by Eric
v3: fix logic screw up

 drivers/pci/pci-sysfs.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 8ecaac9..ea25e5b 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -23,6 +23,7 @@
 #include <linux/mm.h>
 #include <linux/fs.h>
 #include <linux/capability.h>
+#include <linux/security.h>
 #include <linux/pci-aspm.h>
 #include <linux/slab.h>
 #include "pci.h"
@@ -368,7 +369,7 @@ pci_read_config(struct file *filp, struct kobject *kobj,
 	u8 *data = (u8*) buf;
 
 	/* Several chips lock up trying to read undefined config space */
-	if (cap_raised(filp->f_cred->cap_effective, CAP_SYS_ADMIN)) {
+	if (security_capable(filp->f_cred, CAP_SYS_ADMIN) == 0) {
 		size = dev->cfg_size;
 	} else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
 		size = 128;
-- 
1.7.3.4
--
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