linux-kernel - Re: [PATCH v2 1/3] binder: handle PID namespace conversion for freeze operation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aXs5Y3xAFKyZr6nd@google.com>
Date: Thu, 29 Jan 2026 10:41:39 +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, 
	boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com, 
	lossin@...nel.org, a.hindborg@...nel.org, tmgross@...ch.edu, dakr@...nel.org, 
	yury.norov@...il.com, vitaly.wool@...sulko.se, tamird@...il.com, 
	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 1/3] binder: handle PID namespace conversion for freeze operation

On Thu, Jan 29, 2026 at 05:41:17PM +0900, jongan.kim@....com wrote:
> From: JongAn Kim <jongan.kim@....com>
> 
> Currently, when a freeze is attempted from a non-init PID namespace,
> there is a possibility that the wrong process in the init namespace
> may be frozen due to PID collision across namespaces.
> 
> For example, if a container with PID namespace has a process with
> PID 100 (which maps to PID 5000 in init namespace), attempting to
> freeze PID 100 from the container could incorrectly match a different
> process with PID 100 in the init namespace.
> 
> This patch fixes the issue by:
> 1. Converting the caller's PID from their namespace to init namespace
> 2. Matching against binder_proc->pid (which stores init namespace TGID)
> 3. Returning -EINVAL for invalid PIDs and -ESRCH for not-found processes
> 
> This change ensures correct PID handling when binder freeze occurs in
> non-init PID namespace.
> 
> Signed-off-by: JongAn Kim <jongan.kim@....com>

> +	rcu_read_lock();
> +	task = pid_task(find_vpid(pid), PIDTYPE_PID);
> +	init_ns_pid = task ? task_tgid_nr_ns(task, &init_pid_ns) : -ESRCH;

You know this is making me think ... here we are obtaining a pointer to
the `struct task_struct`, then we convert it to a pid, and we compare
with the pid of the binder_proc's task.

Why not just outright compare the `struct task_struct` pointers?

Alice