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fs,userns: Change inode_capable to capable_wrt_inode_uidgid

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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@mit.edu>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: stable@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andy Lutomirski 2014-06-10 12:45:42 -07:00 committed by Linus Torvalds
parent 5b174fd647
commit 23adbe12ef
6 changed files with 27 additions and 26 deletions
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8
fs/attr.c
View File

@ -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;
}

10
fs/inode.c
View File

@ -1839,14 +1839,18 @@ 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;
}

11
fs/namei.c
View File

@ -332,10 +332,11 @@ 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;
}
@ -345,7 +346,7 @@ 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;
/*
@ -353,7 +354,7 @@ 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;
@ -2379,7 +2380,7 @@ 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);
}
/*

2
fs/xfs/xfs_ioctl.c
View File

@ -1215,7 +1215,7 @@ 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);
/*

2
include/linux/capability.h
View File

@ -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 */

20
kernel/capability.c
View File

@ -424,23 +424,19 @@ 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);