fs,userns: Change inode_capable to capable_wrt_inode_uidgid

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>

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/attr.c b/fs/attr.c
index 5d4e59d56e85..6530ced19697 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;
         }