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

BugLink: https://bugs.launchpad.net/bugs/1919492
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>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

diff --git a/security/commoncap.c b/security/commoncap.c
index 6cafb1913f5d314867394bd59fff17d578a66991..e8f9db8f3fdff9e76f5d67cc9c2d41968bbc4b54 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)