From: Ondrej Mosnacek <omosnace@redhat.com>
To: selinux@vger.kernel.org, Paul Moore <paul@paul-moore.com>,
cgroups@vger.kernel.org, Tejun Heo <tj@kernel.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>,
Li Zefan <lizefan@huawei.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Ondrej Mosnacek <omosnace@redhat.com>
Subject: [RFC PATCH 3/3] selinux: do not override context on context mounts
Date: Thu, 13 Dec 2018 15:17:39 +0100 [thread overview]
Message-ID: <20181213141739.8534-4-omosnace@redhat.com> (raw)
In-Reply-To: <20181213141739.8534-1-omosnace@redhat.com>
Ignore all selinux_inode_notifysecctx() calls on mounts with the
SECURITY_FS_USE_MNTPOINT behavior.
This fixes behavior of kernfs-based filesystems when mounted with the
'context=' option. Before this patch, if a node's context had been
explicitly set to a non-default value and later the filesystem has been
remounted with the 'context=' option, then this node would show up as
having a different context.
Steps to reproduce:
# mount -t cgroup2 cgroup2 /sys/fs/cgroup/unified
# chcon unconfined_u:object_r:user_home_t:s0 /sys/fs/cgroup/unified/cgroup.stat
# ls -lZ /sys/fs/cgroup/unified
total 0
-r--r--r--. 1 root root system_u:object_r:cgroup_t:s0 0 Dec 13 10:41 cgroup.controllers
-rw-r--r--. 1 root root system_u:object_r:cgroup_t:s0 0 Dec 13 10:41 cgroup.max.depth
-rw-r--r--. 1 root root system_u:object_r:cgroup_t:s0 0 Dec 13 10:41 cgroup.max.descendants
-rw-r--r--. 1 root root system_u:object_r:cgroup_t:s0 0 Dec 13 10:41 cgroup.procs
-r--r--r--. 1 root root unconfined_u:object_r:user_home_t:s0 0 Dec 13 10:41 cgroup.stat
-rw-r--r--. 1 root root system_u:object_r:cgroup_t:s0 0 Dec 13 10:41 cgroup.subtree_control
-rw-r--r--. 1 root root system_u:object_r:cgroup_t:s0 0 Dec 13 10:41 cgroup.threads
# umount /sys/fs/cgroup/unified
# mount -o context=system_u:object_r:tmpfs_t:s0 -t cgroup2 cgroup2 /sys/fs/cgroup/unified
Result before:
# ls -lZ /sys/fs/cgroup/unified
total 0
-r--r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.controllers
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.max.depth
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.max.descendants
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.procs
-r--r--r--. 1 root root unconfined_u:object_r:user_home_t:s0 0 Dec 13 10:41 cgroup.stat
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.subtree_control
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.threads
Result after:
# ls -lZ /sys/fs/cgroup/unified
total 0
-r--r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.controllers
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.max.depth
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.max.descendants
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.procs
-r--r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.stat
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.subtree_control
-rw-r--r--. 1 root root system_u:object_r:tmpfs_t:s0 0 Dec 13 10:41 cgroup.threads
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
---
security/selinux/hooks.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index d6d29ec54eab..0ca5ed30afe1 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6620,6 +6620,13 @@ static void selinux_inode_invalidate_secctx(struct inode *inode)
*/
static int selinux_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
{
+ struct superblock_security_struct *sbsec = inode->i_sb->s_security;
+
+ /* Do not change context in SECURITY_FS_USE_MNTPOINT case */
+ if ((sbsec->flags & SE_SBINITIALIZED) &&
+ (sbsec->behavior == SECURITY_FS_USE_MNTPOINT))
+ return 0;
+
return selinux_inode_setsecurity(inode, XATTR_SELINUX_SUFFIX, ctx, ctxlen, 0);
}
--
2.19.2
next prev parent reply other threads:[~2018-12-13 14:19 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-13 14:17 [RFC PATCH 0/3] Fix SELinux context mount with the cgroup filesystem Ondrej Mosnacek
2018-12-13 14:17 ` [RFC PATCH 1/3] cgroup: fix parsing empty mount option string Ondrej Mosnacek
2018-12-13 16:03 ` Tejun Heo
2018-12-28 15:14 ` Ondrej Mosnacek
2018-12-28 18:32 ` Tejun Heo
2018-12-13 14:17 ` [RFC PATCH 2/3] selinux: never allow relabeling on context mounts Ondrej Mosnacek
2018-12-13 16:18 ` Stephen Smalley
2018-12-18 15:38 ` Ondrej Mosnacek
2018-12-13 14:17 ` Ondrej Mosnacek [this message]
2018-12-13 16:27 ` [RFC PATCH 3/3] selinux: do not override context " Stephen Smalley
2018-12-18 15:50 ` Ondrej Mosnacek
2018-12-18 19:22 ` Stephen Smalley
2018-12-19 11:44 ` Ondrej Mosnacek
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