linux-kernel - Re: [PATCH v2 3/3] rust_binder: handle PID namespace conversion for freeze operation

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Message-ID: <aXs4B7Rib0_dBNSY@google.com>
Date: Thu, 29 Jan 2026 10:35:51 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: jongan.kim@....com
Cc: arve@...roid.com, brauner@...nel.org, cmllamas@...gle.com, 
	gregkh@...uxfoundation.org, tkjos@...roid.com, ojeda@...nel.org, 
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	viresh.kumar@...aro.org, daniel.almeida@...labora.com, 
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org, 
	heesu0025.kim@....com, ht.hong@....com, jungsu.hwang@....com, 
	kernel-team@...roid.com, sanghun.lee@....com, seulgi.lee@....com, 
	sunghoon.kim@....com
Subject: Re: [PATCH v2 3/3] rust_binder: handle PID namespace conversion for
 freeze operation

On Thu, Jan 29, 2026 at 05:41:19PM +0900, jongan.kim@....com wrote:
> From: HeeSu Kim <heesu0025.kim@....com>
> 
> Port PID namespace conversion logic from C binder to the Rust
> implementation.
> 
> Without namespace conversion, freeze operations from non-init namespaces
> can match wrong processes due to PID collision. This adds proper
> conversion to ensure freeze operations target the correct process.
> 
> Signed-off-by: HeeSu Kim <heesu0025.kim@....com>

Overall looks good, thanks!

> +/// Convert a PID from the current namespace to the global (init) namespace.
> +fn convert_to_init_ns_tgid(pid: u32) -> Result<i32> {

Let's use the typedef task::Pid (of bindings::pid_t) here, so you can
avoid the `init_ns_pid as _` cast below.

> +    let current = kernel::current!();
> +    let init_ns = init_pid_ns();
> +
> +    if current.active_pid_ns().map(|ns| ns.as_ptr()) == Some(init_ns.as_ptr()) {

I'd like to avoid comparing raw pointers for this. Perhaps we should just provide
an implementation of `==` for PidNamespace that compares the address?

Alice