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clone: add CLONE_NNP

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Add a new clone3() flag CLONE_NNP that sets no_new_privs on the child
process at clone time. This is analogous to prctl(PR_SET_NO_NEW_PRIVS)
but applied at process creation rather than requiring a separate step
after the child starts running.

CLONE_NNP is rejected with CLONE_THREAD. It's conceptually a lot simpler
if the whole thread-group is forced into NNP and not have single threads
running around with NNP.

Link: https://patch.msgid.link/20260226-work-pidfs-autoreap-v5-2-d148b984a989@kernel.org
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner
2026-02-26 14:51:00 +01:00
parent 12ae2c81b2
commit 24baca56fa
2 changed files with 10 additions and 1 deletions
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1
include/uapi/linux/sched.h
View File

@@ -37,6 +37,7 @@
#define CLONE_CLEAR_SIGHAND (1ULL << 32) /* Clear any signal handler and reset to SIG_DFL. */
#define CLONE_INTO_CGROUP (1ULL << 33) /* Clone into a specific cgroup given the right permissions. */
#define CLONE_AUTOREAP (1ULL << 34) /* Auto-reap child on exit. */
#define CLONE_NNP (1ULL << 35) /* Set no_new_privs on child. */
/*
* cloning flags intersect with CSIGNAL so can be used with unshare and clone3

10
kernel/fork.c
View File

@@ -2040,6 +2040,11 @@ __latent_entropy struct task_struct *copy_process(
if ((clone_flags & CLONE_PARENT) && current->signal->autoreap)
return ERR_PTR(-EINVAL);
if (clone_flags & CLONE_NNP) {
if (clone_flags & CLONE_THREAD)
return ERR_PTR(-EINVAL);
}
/*
* Force any signals received before this point to be delivered
* before the fork happens. Collect up signals sent to multiple
@@ -2424,6 +2429,9 @@ __latent_entropy struct task_struct *copy_process(
*/
copy_seccomp(p);
if (clone_flags & CLONE_NNP)
task_set_no_new_privs(p);
init_task_pid_links(p);
if (likely(p->pid)) {
ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
@@ -2912,7 +2920,7 @@ static bool clone3_args_valid(struct kernel_clone_args *kargs)
/* Verify that no unknown flags are passed along. */
if (kargs->flags &
~(CLONE_LEGACY_FLAGS | CLONE_CLEAR_SIGHAND | CLONE_INTO_CGROUP |
CLONE_AUTOREAP))
CLONE_AUTOREAP | CLONE_NNP))
return false;
/*