Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")

commit 3b0c2d3eaa83da259d7726192cf55a137769012f upstream.

It turns out that there are in fact userspace implementations that
care and this recent change caused a regression.

https://github.com/containers/buildah/issues/3071

As the motivation for the original change was future development,
and the impact is existing real world code just revert this change
and allow the ambiguity in v3 file caps.

Cc: stable@vger.kernel.org
Fixes: 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/commoncap.c b/security/commoncap.c
index 78598be45f101d46d2fcc4177494a982195269f2..26c1cb725dcbe5c59197cc1e962a60d370a0deb6 100644 (file)
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -500,8 +500,7 @@ int cap_convert_nscap(struct dentry *dentry, const void **ivalue, size_t size)
        __u32 magic, nsmagic;
        struct inode *inode = d_backing_inode(dentry);
        struct user_namespace *task_ns = current_user_ns(),
-               *fs_ns = inode->i_sb->s_user_ns,
-               *ancestor;
+               *fs_ns = inode->i_sb->s_user_ns;
        kuid_t rootid;
        size_t newsize;
 
@@ -524,15 +523,6 @@ int cap_convert_nscap(struct dentry *dentry, const void **ivalue, size_t size)
        if (nsrootid == -1)
                return -EINVAL;
 
-       /*
-        * Do not allow allow adding a v3 filesystem capability xattr
-        * if the rootid field is ambiguous.
-        */
-       for (ancestor = task_ns->parent; ancestor; ancestor = ancestor->parent) {
-               if (from_kuid(ancestor, rootid) == 0)
-                       return -EINVAL;
-       }
-
        newsize = sizeof(struct vfs_ns_cap_data);
        nscap = kmalloc(newsize, GFP_ATOMIC);
        if (!nscap)