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    Subject[PATCH 3.11 91/93] fs,userns: Change inode_capable to capable_wrt_inode_uidgid
    Date
    3.11.10.12 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andy Lutomirski <luto@amacapital.net>

    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@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>
    [ luis: backported to 3.11: based on 3.10 backport ]
    Signed-off-by: Luis Henriques <luis.henriques@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 8dd5825ec708..66fa6251c398 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 d6dfb09c8280..28f29a2b42a4 100644
    --- a/fs/inode.c
    +++ b/fs/inode.c
    @@ -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;
    }
    diff --git a/fs/namei.c b/fs/namei.c
    index b8f1f7f6c75a..2a2d0236f82a 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;
    @@ -2198,7 +2199,7 @@ 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 d9a4f7f40f32..15f90929fb51 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 f6c2ce5701e1..d52eecc0942b 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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