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@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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -50,14 +50,14 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr)
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if ((ia_valid & ATTR_UID) &&
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(!uid_eq(current_fsuid(), inode->i_uid) ||
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!uid_eq(attr->ia_uid, inode->i_uid)) &&
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!inode_capable(inode, CAP_CHOWN))
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!capable_wrt_inode_uidgid(inode, CAP_CHOWN))
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return -EPERM;
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/* Make sure caller can chgrp. */
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if ((ia_valid & ATTR_GID) &&
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(!uid_eq(current_fsuid(), inode->i_uid) ||
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(!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
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!inode_capable(inode, CAP_CHOWN))
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!capable_wrt_inode_uidgid(inode, CAP_CHOWN))
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return -EPERM;
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/* Make sure a caller can chmod. */
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@ -67,7 +67,7 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr)
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/* Also check the setgid bit! */
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if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
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inode->i_gid) &&
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!inode_capable(inode, CAP_FSETID))
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!capable_wrt_inode_uidgid(inode, CAP_FSETID))
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attr->ia_mode &= ~S_ISGID;
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}
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@ -160,7 +160,7 @@ void setattr_copy(struct inode *inode, const struct iattr *attr)
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umode_t mode = attr->ia_mode;
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if (!in_group_p(inode->i_gid) &&
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!inode_capable(inode, CAP_FSETID))
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!capable_wrt_inode_uidgid(inode, CAP_FSETID))
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mode &= ~S_ISGID;
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inode->i_mode = mode;
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}
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10
fs/inode.c
10
fs/inode.c
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@ -1837,14 +1837,18 @@ EXPORT_SYMBOL(inode_init_owner);
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* inode_owner_or_capable - check current task permissions to inode
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* @inode: inode being checked
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*
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* Return true if current either has CAP_FOWNER to the inode, or
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* owns the file.
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* Return true if current either has CAP_FOWNER in a namespace with the
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* inode owner uid mapped, or owns the file.
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*/
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bool inode_owner_or_capable(const struct inode *inode)
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{
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struct user_namespace *ns;
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if (uid_eq(current_fsuid(), inode->i_uid))
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return true;
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if (inode_capable(inode, CAP_FOWNER))
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ns = current_user_ns();
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if (ns_capable(ns, CAP_FOWNER) && kuid_has_mapping(ns, inode->i_uid))
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return true;
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return false;
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}
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11
fs/namei.c
11
fs/namei.c
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@ -321,10 +321,11 @@ int generic_permission(struct inode *inode, int mask)
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if (S_ISDIR(inode->i_mode)) {
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/* DACs are overridable for directories */
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if (inode_capable(inode, CAP_DAC_OVERRIDE))
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if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
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return 0;
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if (!(mask & MAY_WRITE))
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if (inode_capable(inode, CAP_DAC_READ_SEARCH))
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if (capable_wrt_inode_uidgid(inode,
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CAP_DAC_READ_SEARCH))
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return 0;
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return -EACCES;
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}
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@ -334,7 +335,7 @@ int generic_permission(struct inode *inode, int mask)
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* at least one exec bit set.
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*/
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if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
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if (inode_capable(inode, CAP_DAC_OVERRIDE))
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if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
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return 0;
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/*
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@ -342,7 +343,7 @@ int generic_permission(struct inode *inode, int mask)
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*/
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mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
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if (mask == MAY_READ)
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if (inode_capable(inode, CAP_DAC_READ_SEARCH))
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if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
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return 0;
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return -EACCES;
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@ -2199,7 +2200,7 @@ static inline int check_sticky(struct inode *dir, struct inode *inode)
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return 0;
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if (uid_eq(dir->i_uid, fsuid))
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return 0;
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return !inode_capable(inode, CAP_FOWNER);
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return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
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}
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/*
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@ -211,7 +211,7 @@ extern bool has_ns_capability_noaudit(struct task_struct *t,
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extern bool capable(int cap);
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extern bool ns_capable(struct user_namespace *ns, int cap);
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extern bool nsown_capable(int cap);
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extern bool inode_capable(const struct inode *inode, int cap);
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extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);
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extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
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/* audit system wants to get cap info from files as well */
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@ -445,22 +445,18 @@ bool nsown_capable(int cap)
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}
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/**
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* inode_capable - Check superior capability over inode
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* capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
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* @inode: The inode in question
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* @cap: The capability in question
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*
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* Return true if the current task has the given superior capability
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* targeted at it's own user namespace and that the given inode is owned
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* by the current user namespace or a child namespace.
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*
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* Currently we check to see if an inode is owned by the current
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* user namespace by seeing if the inode's owner maps into the
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* current user namespace.
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*
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* Return true if the current task has the given capability targeted at
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* its own user namespace and that the given inode's uid and gid are
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* mapped into the current user namespace.
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*/
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bool inode_capable(const struct inode *inode, int cap)
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bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
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{
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struct user_namespace *ns = current_user_ns();
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return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid);
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return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) &&
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kgid_has_mapping(ns, inode->i_gid);
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}
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