[PATCH v3 3/3] rust_binder: handle PID namespace conversion for freeze operation

[jongan.kim@lge.com]

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.

Signed-off-by: HeeSu Kim <heesu0025.kim@lge.com>
---
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/process.rs | 37 +++++++++++++++++++++++++++----
 1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/drivers/android/binder/process.rs b/drivers/android/binder/process.rs
index 132055b4790f..ea30bfac2e0b 100644
--- a/drivers/android/binder/process.rs
+++ b/drivers/android/binder/process.rs
@@ -22,6 +22,8 @@
     id_pool::IdPool,
     list::{List, ListArc, ListArcField, ListLinks},
     mm,
+    pid::Pid,
+    pid_namespace::PidNamespace,
     prelude::*,
     rbtree::{self, RBTree, RBTreeNode, RBTreeNodeReservation},
     seq_file::SeqFile,
@@ -29,9 +31,9 @@
     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 +1500,42 @@ pub(crate) fn ioctl_freeze(&self, info: &BinderFreezeInfo) -> Result {
     }
 }
 
+/// Convert a PID from the current namespace to the global (init) namespace.
+fn convert_to_init_ns_tgid(pid: PidT) -> Result<PidT> {
+    let current = kernel::current!();
+    let init_ns = PidNamespace::init_ns();
+
+    if current.active_pid_ns() == Some(init_ns) {
+        // Already in init namespace.
+        return Ok(pid);
+    }
+
+    if pid == 0 {
+        return Err(EINVAL);
+    }
+
+    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(task.group_leader().pid())
+}
+
 fn get_frozen_status(data: UserSlice) -> Result {
     let (mut reader, mut writer) = data.reader_writer();
 
     let mut info = reader.read::<BinderFrozenStatusInfo>()?;
+
+    let init_ns_pid = convert_to_init_ns_tgid(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 proc.task.pid() == init_ns_pid as _ {
                 found = true;
                 let inner = proc.inner.lock();
                 let txns_pending = inner.txns_pending_locked();
@@ -1530,13 +1557,15 @@ fn get_frozen_status(data: UserSlice) -> Result {
 fn ioctl_freeze(reader: &mut UserSliceReader) -> Result {
     let info = reader.read::<BinderFreezeInfo>()?;
 
+    let init_ns_pid = convert_to_init_ns_tgid(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)? {
+        for proc in ctx.get_procs_with_pid(init_ns_pid)? {
             procs.push(proc, GFP_KERNEL)?;
         }
     }
-- 
2.25.1