[3.8.y.z extended stable] Patch "fs, userns: Change inode_capable to capable_wrt_inode_uidgid" has been added to staging queue
Kamal Mostafa
kamal at canonical.com
Thu Jul 24 19:27:32 UTC 2014
This is a note to let you know that I have just added a patch titled
fs,userns: Change inode_capable to capable_wrt_inode_uidgid
to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue
This patch is scheduled to be released in version 3.8.13.27.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
------
>From 010698384c4d282510f95f41614ae0f02dbdaad3 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto at amacapital.net>
Date: Tue, 10 Jun 2014 12:45:42 -0700
Subject: 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.
Cc: Theodore Ts'o <tytso at mit.edu>
Cc: Serge Hallyn <serge.hallyn at ubuntu.com>
Cc: "Eric W. Biederman" <ebiederm at xmission.com>
Cc: Dave Chinner <david at fromorbit.com>
Signed-off-by: Andy Lutomirski <luto at amacapital.net>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
[ kamal: backport to 3.8-stable: dropped inapplicable xfs change ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
fs/attr.c | 8 ++++----
fs/inode.c | 10 +++++++---
fs/namei.c | 11 ++++++-----
include/linux/capability.h | 2 +-
kernel/capability.c | 18 +++++++-----------
5 files changed, 25 insertions(+), 24 deletions(-)
diff --git a/fs/attr.c b/fs/attr.c
index 1449adb..6a54f13 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 b98540e..2e4031e 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1842,14 +1842,18 @@ 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 77dc200..8bbff22 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;
@@ -2208,7 +2209,7 @@ 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/include/linux/capability.h b/include/linux/capability.h
index d9a4f7f..15f9092 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -211,7 +211,7 @@ extern bool has_ns_capability_noaudit(struct task_struct *t,
extern bool capable(int cap);
extern bool ns_capable(struct user_namespace *ns, int cap);
extern bool nsown_capable(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 f6c2ce5..d52eecc0 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -445,22 +445,18 @@ bool nsown_capable(int cap)
}
/**
- * 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);
}
--
1.9.1
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