Re: [PATCH net] netdev-genl: report NAPI thread PID in the caller's pid namespace

[Samiullah Khawaja <skhawaja@google.com>]

On Tue, Jun 16, 2026 at 01:17:36AM +0800, Maoyi Xie wrote:
>netdev_nl_napi_fill_one() reports the NAPI kthread PID in NETDEV_A_NAPI_PID
>using task_pid_nr(), which returns the PID in the initial pid namespace.
>
>NETDEV_CMD_NAPI_GET does not have GENL_ADMIN_PERM and the netdev genl family
>is netnsok, so a caller in a child pid namespace can issue it. That caller
>then sees the kthread's global PID, even though the kthread is not visible
>in its pid namespace, where the value should be 0.
>
>Translate the PID through the caller's pid namespace, the same way commit
>3799c2570982 ("io_uring/fdinfo: translate SqThread PID through caller's
>pid_ns") did for the io_uring SQPOLL thread. The doit and dumpit paths both
>run synchronously in the caller's context, so task_active_pid_ns(current) is
>the caller's pid namespace.
>
>Fixes: db4704f4e4df ("netdev-genl: Add PID for the NAPI thread")
>Cc: stable@vger.kernel.org
>Signed-off-by: Maoyi Xie <maoyixie.tju@gmail.com>
>---
> net/core/netdev-genl.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
>diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
>index b8f6076d8007..4c23e985cc01 100644
>--- a/net/core/netdev-genl.c
>+++ b/net/core/netdev-genl.c
>@@ -2,6 +2,7 @@
>
> #include <linux/netdevice.h>
> #include <linux/notifier.h>
>+#include <linux/pid_namespace.h>
> #include <linux/rtnetlink.h>
> #include <net/busy_poll.h>
> #include <net/net_namespace.h>
>@@ -189,7 +190,8 @@ netdev_nl_napi_fill_one(struct sk_buff *rsp, struct napi_struct *napi,
> 		goto nla_put_failure;
>
> 	if (napi->thread) {
>-		pid = task_pid_nr(napi->thread);
>+		pid = task_pid_nr_ns(napi->thread,
>+				     task_active_pid_ns(current));
> 		if (nla_put_u32(rsp, NETDEV_A_NAPI_PID, pid))
> 			goto nla_put_failure;
> 	}
>--
>2.43.0
>

Reviewed-by: Samiullah Khawaja <skhawaja@google.com>