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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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10
fs/inode.c
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@@ -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;
}