fs-userns: CVE-2014-4014

Fixes a potential privilege escalation flaw when the Linux
kernel is built with the user namespaces(CONFIG_USER_NS)

References:
http://www.openwall.com/lists/oss-security/2014/06/10/4
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-4014

Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>

2 files changed, 211 insertions, 0 deletions

diff --git a/recipes-kernel/linux/files/fs-CVE-2014-4014.patch b/recipes-kernel/linux/files/fs-CVE-2014-4014.patch
new file mode 100644
index 0000000..a61ae4c
--- /dev/null
+++ b/recipes-kernel/linux/files/fs-CVE-2014-4014.patch
@@ -0,0 +1,210 @@
+From 2246a472bce19c0d373fb5488a0e612e3328ce0a Mon Sep 17 00:00:00 2001
+From: Andy Lutomirski <luto@amacapital.net>
+Date: Tue, 10 Jun 2014 12:45:42 -0700
+Subject: [PATCH] fs,userns: Change inode_capable to capable_wrt_inode_uidgid
+
+commit 23adbe12ef7d3d4195e80800ab36b37bee28cd03 upstream.
+
+The kernel has no concept of capabilities with respect to inodes; inodes
+exist independently of namespaces.  For example, inode_capable(inode,
+CAP_LINUX_IMMUTABLE) would be nonsense.
+
+This patch changes inode_capable to check for uid and gid mappings and
+renames it to capable_wrt_inode_uidgid, which should make it more
+obvious what it does.
+
+Fixes CVE-2014-4014.
+Upstream-Status: Backport
+
+Cc: Theodore Ts'o <tytso@mit.edu>
+Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
+Cc: "Eric W. Biederman" <ebiederm@xmission.com>
+Cc: Dave Chinner <david@fromorbit.com>
+Signed-off-by: Andy Lutomirski <luto@amacapital.net>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Jiri Slaby <jslaby@suse.cz>
+Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
+---
+ fs/attr.c                  |  8 ++++----
+ fs/inode.c                 | 10 +++++++---
+ fs/namei.c                 | 11 ++++++-----
+ fs/xfs/xfs_ioctl.c         |  2 +-
+ include/linux/capability.h |  2 +-
+ kernel/capability.c        | 20 ++++++++------------
+ 6 files changed, 27 insertions(+), 26 deletions(-)
+
+diff --git a/fs/attr.c b/fs/attr.c
+index 8dd5825..66fa625 100644
+--- a/fs/attr.c
++++ b/fs/attr.c
+@@ -50,14 +50,14 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr)
+        if ((ia_valid & ATTR_UID) &&
+            (!uid_eq(current_fsuid(), inode->i_uid) ||
+             !uid_eq(attr->ia_uid, inode->i_uid)) &&
+-           !inode_capable(inode, CAP_CHOWN))
++           !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
+                return -EPERM;
+ 
+        /* Make sure caller can chgrp. */
+        if ((ia_valid & ATTR_GID) &&
+            (!uid_eq(current_fsuid(), inode->i_uid) ||
+            (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
+-           !inode_capable(inode, CAP_CHOWN))
++           !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
+                return -EPERM;
+ 
+        /* Make sure a caller can chmod. */
+@@ -67,7 +67,7 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr)
+                /* Also check the setgid bit! */
+                if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
+                                inode->i_gid) &&
+-                   !inode_capable(inode, CAP_FSETID))
++                   !capable_wrt_inode_uidgid(inode, CAP_FSETID))
+                        attr->ia_mode &= ~S_ISGID;
+        }
+ 
+@@ -160,7 +160,7 @@ void setattr_copy(struct inode *inode, const struct iattr *attr)
+                umode_t mode = attr->ia_mode;
+ 
+                if (!in_group_p(inode->i_gid) &&
+-                   !inode_capable(inode, CAP_FSETID))
++                   !capable_wrt_inode_uidgid(inode, CAP_FSETID))
+                        mode &= ~S_ISGID;
+                inode->i_mode = mode;
+        }
+diff --git a/fs/inode.c b/fs/inode.c
+index b33ba8e..1e6e846 100644
+--- a/fs/inode.c
++++ b/fs/inode.c
+@@ -1808,14 +1808,18 @@ EXPORT_SYMBOL(inode_init_owner);
+  * inode_owner_or_capable - check current task permissions to inode
+  * @inode: inode being checked
+  *
+- * Return true if current either has CAP_FOWNER to the inode, or
+- * owns the file.
++ * Return true if current either has CAP_FOWNER in a namespace with the
++ * inode owner uid mapped, or owns the file.
+  */
+ bool inode_owner_or_capable(const struct inode *inode)
+ {
++       struct user_namespace *ns;
++
+        if (uid_eq(current_fsuid(), inode->i_uid))
+                return true;
+-       if (inode_capable(inode, CAP_FOWNER))
++
++       ns = current_user_ns();
++       if (ns_capable(ns, CAP_FOWNER) && kuid_has_mapping(ns, inode->i_uid))
+                return true;
+        return false;
+ }
+diff --git a/fs/namei.c b/fs/namei.c
+index 187cacf..338d08b 100644
+--- a/fs/namei.c
++++ b/fs/namei.c
+@@ -321,10 +321,11 @@ int generic_permission(struct inode *inode, int mask)
+ 
+        if (S_ISDIR(inode->i_mode)) {
+                /* DACs are overridable for directories */
+-               if (inode_capable(inode, CAP_DAC_OVERRIDE))
++               if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
+                        return 0;
+                if (!(mask & MAY_WRITE))
+-                       if (inode_capable(inode, CAP_DAC_READ_SEARCH))
++                       if (capable_wrt_inode_uidgid(inode,
++                                                    CAP_DAC_READ_SEARCH))
+                                return 0;
+                return -EACCES;
+        }
+@@ -334,7 +335,7 @@ int generic_permission(struct inode *inode, int mask)
+         * at least one exec bit set.
+         */
+        if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
+-               if (inode_capable(inode, CAP_DAC_OVERRIDE))
++               if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
+                        return 0;
+ 
+        /*
+@@ -342,7 +343,7 @@ int generic_permission(struct inode *inode, int mask)
+         */
+        mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
+        if (mask == MAY_READ)
+-               if (inode_capable(inode, CAP_DAC_READ_SEARCH))
++               if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
+                        return 0;
+ 
+        return -EACCES;
+@@ -2404,7 +2405,7 @@ static inline int check_sticky(struct inode *dir, struct inode *inode)
+                return 0;
+        if (uid_eq(dir->i_uid, fsuid))
+                return 0;
+-       return !inode_capable(inode, CAP_FOWNER);
++       return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
+ }
+ 
+ /*
+diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
+index 8c8ef24..52b5375 100644
+--- a/fs/xfs/xfs_ioctl.c
++++ b/fs/xfs/xfs_ioctl.c
+@@ -1133,7 +1133,7 @@ xfs_ioctl_setattr(
+                 * cleared upon successful return from chown()
+                 */
+                if ((ip->i_d.di_mode & (S_ISUID|S_ISGID)) &&
+-                   !inode_capable(VFS_I(ip), CAP_FSETID))
++                   !capable_wrt_inode_uidgid(VFS_I(ip), CAP_FSETID))
+                        ip->i_d.di_mode &= ~(S_ISUID|S_ISGID);
+ 
+                /*
+diff --git a/include/linux/capability.h b/include/linux/capability.h
+index a6ee1f9..84b13ad 100644
+--- a/include/linux/capability.h
++++ b/include/linux/capability.h
+@@ -210,7 +210,7 @@ extern bool has_ns_capability_noaudit(struct task_struct *t,
+                                      struct user_namespace *ns, int cap);
+ extern bool capable(int cap);
+ extern bool ns_capable(struct user_namespace *ns, int cap);
+-extern bool inode_capable(const struct inode *inode, int cap);
++extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);
+ extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
+ 
+ /* audit system wants to get cap info from files as well */
+diff --git a/kernel/capability.c b/kernel/capability.c
+index 4e66bf9..788653b 100644
+--- a/kernel/capability.c
++++ b/kernel/capability.c
+@@ -433,23 +433,19 @@ bool capable(int cap)
+ EXPORT_SYMBOL(capable);
+ 
+ /**
+- * inode_capable - Check superior capability over inode
++ * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
+  * @inode: The inode in question
+  * @cap: The capability in question
+  *
+- * Return true if the current task has the given superior capability
+- * targeted at it's own user namespace and that the given inode is owned
+- * by the current user namespace or a child namespace.
+- *
+- * Currently we check to see if an inode is owned by the current
+- * user namespace by seeing if the inode's owner maps into the
+- * current user namespace.
+- *
++ * Return true if the current task has the given capability targeted at
++ * its own user namespace and that the given inode's uid and gid are
++ * mapped into the current user namespace.
+  */
+-bool inode_capable(const struct inode *inode, int cap)
++bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
+ {
+        struct user_namespace *ns = current_user_ns();
+ 
+-       return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid);
++       return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) &&
++               kgid_has_mapping(ns, inode->i_gid);
+ }
+-EXPORT_SYMBOL(inode_capable);
++EXPORT_SYMBOL(capable_wrt_inode_uidgid);
+-- 
+1.9.1
+
diff --git a/recipes-kernel/linux/linux-qoriq_3.12.bb b/recipes-kernel/linux/linux-qoriq_3.12.bb
index 9727a73..527daf4 100644
--- a/recipes-kernel/linux/linux-qoriq_3.12.bb
+++ b/recipes-kernel/linux/linux-qoriq_3.12.bb
@@ -34,6 +34,7 @@ SRC_URI = "git://git.freescale.com/ppc/sdk/linux.git;nobranch=1 \
     file://0001-shmem-CVE-2014-4171.patch \
     file://0002-shmem-CVE-2014-4171.patch \
     file://0003-shmem-CVE-2014-4171.patch \
+    file://fs-CVE-2014-4014.patch \
 "
 SRCREV = "6619b8b55796cdf0cec04b66a71288edd3057229"