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Date: Fri,  6 Feb 2026 17:53:36 +0900
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Subject: [PATCH v4 3/3] rust_binder: fix PID namespace collision for freeze operation

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.

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@...yguo.net>
Link: https://lore.kernel.org/rust-for-linux/DG5CFX3ML5YL.2FE913F20LNPT@garyguo.net/
Suggested-by: Alice Ryhl <aliceryhl@...gle.com>
Link: https://lore.kernel.org/lkml/aXs5Y3xAFKyZr6nd@google.com/
Signed-off-by: Heesu Kim <heesu0025.kim@....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) {
+                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) {
                 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 {
-- 
2.25.1

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