Re: [PATCH v4 3/3] rust_binder: fix PID namespace collision for freeze operation

["Gary Guo" <gary@garyguo.net>]

On Fri Feb 6, 2026 at 8:53 AM GMT, jongan.kim wrote:
> From: HeeSu Kim <heesu0025.kim@lge.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.
>
> This patch fixes the issue by:
> - Add get_task_from_vpid() to translate VPID to Task reference
> - Add Context::get_procs_with_task() for Task-based process lookup
>   using &mut KVec parameter to avoid intermediate allocations
> - Update get_frozen_status() and ioctl_freeze() to use Task comparison
>
> Suggested-by: Gary Guo <gary@garyguo.net>
> Link: https://lore.kernel.org/rust-for-linux/DG5CFX3ML5YL.2FE913F20LNPT@garyguo.net/
> Suggested-by: Alice Ryhl <aliceryhl@google.com>
> Link: https://lore.kernel.org/lkml/aXs5Y3xAFKyZr6nd@google.com/
> Signed-off-by: Heesu Kim <heesu0025.kim@lge.com>
> ---
> v3 -> v4
> - change subject name more clearly
> - Use Task pointer comparison instead of PID number comparison
> - Remove PidNamespace dependency entirely
> - Use &mut KVec parameter to avoid intermediate allocation
> - Merge context.rs and process.rs changes into single patch
>  
> v2 -> v3:
> - Use task::Pid typedef instead of u32/i32
> - Use PidNamespace::init_ns() instead of init_pid_ns()
> - Compare PidNamespace directly with == instead of raw pointers
> - Use Pid::find_vpid() and pid.pid_task() (dropped _with_guard suffix)
> - Fix rustfmt import ordering (rcu before Arc)
> - Rename TaskPid alias to PidT for clearer pid_t type indication
> - Use task.group_leader().pid() instead of tgid_nr_ns() for consistency with C
>
>  drivers/android/binder/context.rs | 16 +++++++++++++++-
>  drivers/android/binder/process.rs | 25 +++++++++++++++++++------
>  2 files changed, 34 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/android/binder/context.rs b/drivers/android/binder/context.rs
> index 3d135ec03ca7..1fc779e4d9ce 100644
> --- a/drivers/android/binder/context.rs
> +++ b/drivers/android/binder/context.rs
> @@ -9,7 +9,7 @@
>      security,
>      str::{CStr, CString},
>      sync::{Arc, Mutex},
> -    task::Kuid,
> +    task::{Kuid, Task},
>  };
>  
>  use crate::{error::BinderError, node::NodeRef, process::Process};
> @@ -177,4 +177,18 @@ pub(crate) fn get_procs_with_pid(&self, pid: i32) -> Result<KVec<Arc<Process>>>
>          }
>          Ok(backing)
>      }
> +
> +    pub(crate) fn get_procs_with_task(
> +        &self,
> +        target: &Task,
> +        out: &mut KVec<Arc<Process>>,
> +    ) -> Result {
> +        let lock = self.manager.lock();
> +        for proc in &lock.all_procs {
> +            if core::ptr::eq(&*proc.task, target) {

I think we should just as a `PartialEq` and `Eq` impl to `Task`.

> +                out.push(Arc::from(proc), GFP_KERNEL)?;
> +            }
> +        }
> +        Ok(())
> +    }
>  }
> diff --git a/drivers/android/binder/process.rs b/drivers/android/binder/process.rs
> index 132055b4790f..58e816f8873f 100644
> --- a/drivers/android/binder/process.rs
> +++ b/drivers/android/binder/process.rs
> @@ -22,6 +22,7 @@
>      id_pool::IdPool,
>      list::{List, ListArc, ListArcField, ListLinks},
>      mm,
> +    pid::Pid,
>      prelude::*,
>      rbtree::{self, RBTree, RBTreeNode, RBTreeNodeReservation},
>      seq_file::SeqFile,
> @@ -29,9 +30,9 @@
>      sync::poll::PollTable,
>      sync::{
>          lock::{spinlock::SpinLockBackend, Guard},
> -        Arc, ArcBorrow, CondVar, CondVarTimeoutResult, Mutex, SpinLock, UniqueArc,
> +        rcu, Arc, ArcBorrow, CondVar, CondVarTimeoutResult, Mutex, SpinLock, UniqueArc,
>      },
> -    task::Task,
> +    task::{Pid as PidT, Task},
>      types::ARef,
>      uaccess::{UserSlice, UserSliceReader},
>      uapi,
> @@ -1498,17 +1499,29 @@ pub(crate) fn ioctl_freeze(&self, info: &BinderFreezeInfo) -> Result {
>      }
>  }
>  
> +/// Get Task reference from VPID with refcount increment.
> +fn get_task_from_vpid(pid: PidT) -> Result<ARef<Task>> {
> +    let rcu_guard = rcu::read_lock();
> +    let pid_struct = Pid::find_vpid(pid, &rcu_guard).ok_or(ESRCH)?;
> +    let task = pid_struct.pid_task(&rcu_guard).ok_or(ESRCH)?;
> +
> +    Ok(ARef::from(task))
> +}
> +
>  fn get_frozen_status(data: UserSlice) -> Result {
>      let (mut reader, mut writer) = data.reader_writer();
>  
>      let mut info = reader.read::<BinderFrozenStatusInfo>()?;
> +
> +    let target_task = get_task_from_vpid(info.pid as PidT)?;
> +
>      info.sync_recv = 0;
>      info.async_recv = 0;
>      let mut found = false;
>  
>      for ctx in crate::context::get_all_contexts()? {
>          ctx.for_each_proc(|proc| {
> -            if proc.task.pid() == info.pid as _ {
> +            if core::ptr::eq(&*proc.task, &*target_task) {

Same here, could use `==` if you have `PartialEq` impl on task.

Best,
Gary

>                  found = true;
>                  let inner = proc.inner.lock();
>                  let txns_pending = inner.txns_pending_locked();
> @@ -1530,15 +1543,15 @@ fn get_frozen_status(data: UserSlice) -> Result {
>  fn ioctl_freeze(reader: &mut UserSliceReader) -> Result {
>      let info = reader.read::<BinderFreezeInfo>()?;
>  
> +    let target_task = get_task_from_vpid(info.pid as PidT)?;
> +
>      // Very unlikely for there to be more than 3, since a process normally uses at most binder and
>      // hwbinder.
>      let mut procs = KVec::with_capacity(3, GFP_KERNEL)?;
>  
>      let ctxs = crate::context::get_all_contexts()?;
>      for ctx in ctxs {
> -        for proc in ctx.get_procs_with_pid(info.pid as i32)? {
> -            procs.push(proc, GFP_KERNEL)?;
> -        }
> +        ctx.get_procs_with_task(&target_task, &mut procs)?;
>      }
>  
>      for proc in procs {