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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
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