[GIT PULL] SELinux list corruption fix for 3.18

From: James Morris
Date: Tue Oct 14 2014 - 11:05:27 EST

This is a fix for list corruption in the SELinux code.

Note that the git-log output is still broken due to the back-merge issue
previously discussed. The fix is in commit

Please pull.


The following changes since commit 2d65a9f48fcdf7866aab6457bc707ca233e0c791:

Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux (2014-10-14 09:39:08 +0200)

are available in the git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git for-linus

James Morris (1):
Merge branch 'stable-3.18' of git://git.infradead.org/users/pcmoore/selinux into for-linus

Jiri Pirko (1):
selinux: register nf hooks with single nf_register_hooks call

Paul Moore (2):
selinux: fix a problem with IPv6 traffic denials in selinux_ip_postroute()
selinux: make the netif cache namespace aware

Richard Guy Briggs (2):
selinux: cleanup error reporting in selinux_nlmsg_perm()
selinux: normalize audit log formatting

Stephen Smalley (2):
selinux: Permit bounded transitions under NO_NEW_PRIVS or NOSUID.
selinux: fix inode security list corruption

security/selinux/hooks.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

commit 7c66bdc72bc3d792886c42bbab4b214c1fe536e0
Author: Stephen Smalley <sds@xxxxxxxxxxxxx>
Date: Mon Oct 6 16:32:52 2014 -0400

selinux: fix inode security list corruption

sb_finish_set_opts() can race with inode_free_security()
when initializing inode security structures for inodes
created prior to initial policy load or by the filesystem
during ->mount(). This appears to have always been
a possible race, but commit 3dc91d4 ("SELinux: Fix possible
NULL pointer dereference in selinux_inode_permission()")
made it more evident by immediately reusing the unioned
list/rcu element of the inode security structure for call_rcu()
upon an inode_free_security(). But the underlying issue
was already present before that commit as a possible use-after-free
of isec.

Shivnandan Kumar reported the list corruption and proposed
a patch to split the list and rcu elements out of the union
as separate fields of the inode_security_struct so that setting
the rcu element would not affect the list element. However,
this would merely hide the issue and not truly fix the code.

This patch instead moves up the deletion of the list entry
prior to dropping the sbsec->isec_lock initially. Then,
if the inode is dropped subsequently, there will be no further
references to the isec.

Reported-by: Shivnandan Kumar <shivnandan.k@xxxxxxxxxxx>
Signed-off-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paul Moore <pmoore@xxxxxxxxxx>

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 29e64d4..2478976 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -481,6 +481,7 @@ next_inode:
struct inode_security_struct, list);
struct inode *inode = isec->inode;
+ list_del_init(&isec->list);
inode = igrab(inode);
if (inode) {
@@ -489,7 +490,6 @@ next_inode:
- list_del_init(&isec->list);
goto next_inode;
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