Quoting Eric W. Biederman (ebied...@xmission.com):
>
> Remove the test for the impossible case where tsk->nsproxy == NULL. Fork
> will never be called with tsk->nsproxy == NULL.
>
> Only call get_nsproxy when we don't need to generate a new_nsproxy,
> and mark the case where we don't generate a new nsproxy as likely.
>
> Remove the code to drop an unnecessarily acquired nsproxy value.
>
> Signed-off-by: "Eric W. Biederman" <ebied...@xmission.com>
Acked-by: Serge Hallyn <serge.hal...@canonical.com>
> ---
> kernel/nsproxy.c | 35 +++++++++++------------------------
> 1 files changed, 11 insertions(+), 24 deletions(-)
>
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index d9afd2563..a1ed011 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -125,22 +125,16 @@ int copy_namespaces(unsigned long flags, struct
> task_struct *tsk)
> struct nsproxy *old_ns = tsk->nsproxy;
> struct user_namespace *user_ns = task_cred_xxx(tsk, user_ns);
> struct nsproxy *new_ns;
> - int err = 0;
>
> - if (!old_ns)
> + if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
> + CLONE_NEWPID | CLONE_NEWNET)))) {
> + get_nsproxy(old_ns);
> return 0;
> -
> - get_nsproxy(old_ns);
> -
> - if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
> - CLONE_NEWPID | CLONE_NEWNET)))
> - return 0;
> -
> - if (!ns_capable(user_ns, CAP_SYS_ADMIN)) {
> - err = -EPERM;
> - goto out;
> }
>
> + if (!ns_capable(user_ns, CAP_SYS_ADMIN))
> + return -EPERM;
> +
> /*
> * CLONE_NEWIPC must detach from the undolist: after switching
> * to a new ipc namespace, the semaphore arrays from the old
> @@ -149,22 +143,15 @@ int copy_namespaces(unsigned long flags, struct
> task_struct *tsk)
> * it along with CLONE_NEWIPC.
> */
> if ((flags & (CLONE_NEWIPC | CLONE_SYSVSEM)) ==
> - (CLONE_NEWIPC | CLONE_SYSVSEM)) {
> - err = -EINVAL;
> - goto out;
> - }
> + (CLONE_NEWIPC | CLONE_SYSVSEM))
> + return -EINVAL;
>
> new_ns = create_new_namespaces(flags, tsk, user_ns, tsk->fs);
> - if (IS_ERR(new_ns)) {
> - err = PTR_ERR(new_ns);
> - goto out;
> - }
> + if (IS_ERR(new_ns))
> + return PTR_ERR(new_ns);
>
> tsk->nsproxy = new_ns;
> -
> -out:
> - put_nsproxy(old_ns);
> - return err;
> + return 0;
> }
>
> void free_nsproxy(struct nsproxy *ns)
> --
> 1.7.5.4
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