| From 23adbe12ef7d3d4195e80800ab36b37bee28cd03 Mon Sep 17 00:00:00 2001 |
| From: Andy Lutomirski <luto@amacapital.net> |
| Date: Tue, 10 Jun 2014 12:45:42 -0700 |
| Subject: fs,userns: Change inode_capable to capable_wrt_inode_uidgid |
| |
| 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> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| 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(-) |
| |
| --- a/fs/attr.c |
| +++ b/fs/attr.c |
| @@ -50,14 +50,14 @@ int inode_change_ok(const struct inode * |
| 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 * |
| /* 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, c |
| 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; |
| } |
| --- a/fs/inode.c |
| +++ b/fs/inode.c |
| @@ -1840,14 +1840,18 @@ 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; |
| } |
| --- a/fs/namei.c |
| +++ b/fs/namei.c |
| @@ -332,10 +332,11 @@ int generic_permission(struct inode *ino |
| |
| 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 *ino |
| * 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 *ino |
| */ |
| 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; |
| @@ -2370,7 +2371,7 @@ static inline int check_sticky(struct in |
| 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); |
| } |
| |
| /* |
| --- a/fs/xfs/xfs_ioctl.c |
| +++ b/fs/xfs/xfs_ioctl.c |
| @@ -1241,7 +1241,7 @@ 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); |
| |
| /* |
| --- a/include/linux/capability.h |
| +++ b/include/linux/capability.h |
| @@ -210,7 +210,7 @@ extern bool has_ns_capability_noaudit(st |
| 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 */ |
| --- 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); |