Quoting Seth Forshee (seth.fors...@canonical.com):
> Currently root is restricted from performing some modifications
> to inodes whose owner is INVALID_UID or group is INVALID_GID
> because this id doesn't map into any user namespace. Add a
> special case to the relevant checks to make sure root is always
> capable of performing these operations.
>
> Signed-off-by: Seth Forshee <seth.fors...@canonical.com>
(A case which was previously not possible.)
Acked-by: Serge E. Hallyn <serge.hal...@ubuntu.com>
> ---
> fs/inode.c | 3 +++
> kernel/capability.c | 6 +++++-
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index 26753ba7b6d6..1029320ff029 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1840,6 +1840,9 @@ bool inode_owner_or_capable(const struct inode *inode)
> {
> struct user_namespace *ns;
>
> + if (capable(CAP_SYS_ADMIN))
> + return true;
> +
> if (uid_eq(current_fsuid(), inode->i_uid))
> return true;
>
> diff --git a/kernel/capability.c b/kernel/capability.c
> index 989f5bfc57dc..a472eaa52b6a 100644
> --- a/kernel/capability.c
> +++ b/kernel/capability.c
> @@ -438,8 +438,12 @@ EXPORT_SYMBOL(capable);
> */
> bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
> {
> - struct user_namespace *ns = current_user_ns();
> + struct user_namespace *ns;
>
> + if (capable(CAP_SYS_ADMIN))
> + return true;
> +
> + ns = current_user_ns();
> return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid) &&
> kgid_has_mapping(ns, inode->i_gid);
> }
> --
> 1.9.1
>
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