binder: don't detect sender/target during buffer cleanup

commit 32e9f56a96d8d0f23cb2aeb2a3cd18d40393e787 upstream.

When freeing txn buffers, binder_transaction_buffer_release()
attempts to detect whether the current context is the target by
comparing current->group_leader to proc->tsk. This is an unreliable
test. Instead explicitly pass an 'is_failure' boolean.

Detecting the sender was being used as a way to tell if the
transaction failed to be sent.  When cleaning up after
failing to send a transaction, there is no need to close
the fds associated with a BINDER_TYPE_FDA object. Now
'is_failure' can be used to accurately detect this case.

Fixes: 44d8047f1d87 ("binder: use standard functions to allocate fds")
Cc: stable <stable@vger.kernel.org>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Link: https://lore.kernel.org/r/20211015233811.3532235-1-tkjos@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 26382e9..49fb741 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -1870,7 +1870,7 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
                binder_dec_node(buffer->target_node, 1, 0);
 
        off_start_offset = ALIGN(buffer->data_size, sizeof(void *));
-       off_end_offset = is_failure ? failed_at :
+       off_end_offset = is_failure && failed_at ? failed_at :
                                off_start_offset + buffer->offsets_size;
        for (buffer_offset = off_start_offset; buffer_offset < off_end_offset;
             buffer_offset += sizeof(binder_size_t)) {
@@ -1956,9 +1956,8 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
                        binder_size_t fd_buf_size;
                        binder_size_t num_valid;
 
-                       if (proc->tsk != current->group_leader) {
+                       if (is_failure) {
                                /*
-                                * Nothing to do if running in sender context
                                 * The fd fixups have not been applied so no
                                 * fds need to be closed.
                                 */
@@ -3176,6 +3175,7 @@ err_invalid_target_handle:
  * binder_free_buf() - free the specified buffer
  * @proc:      binder proc that owns buffer
  * @buffer:    buffer to be freed
+ * @is_failure:        failed to send transaction
  *
  * If buffer for an async transaction, enqueue the next async
  * transaction from the node.
@@ -3185,7 +3185,7 @@ err_invalid_target_handle:
 static void
 binder_free_buf(struct binder_proc *proc,
                struct binder_thread *thread,
-               struct binder_buffer *buffer)
+               struct binder_buffer *buffer, bool is_failure)
 {
        binder_inner_proc_lock(proc);
        if (buffer->transaction) {
@@ -3213,7 +3213,7 @@ binder_free_buf(struct binder_proc *proc,
                binder_node_inner_unlock(buf_node);
        }
        trace_binder_transaction_buffer_release(buffer);
-       binder_transaction_buffer_release(proc, thread, buffer, 0, false);
+       binder_transaction_buffer_release(proc, thread, buffer, 0, is_failure);
        binder_alloc_free_buf(&proc->alloc, buffer);
 }
 
@@ -3415,7 +3415,7 @@ static int binder_thread_write(struct binder_proc *proc,
                                     proc->pid, thread->pid, (u64)data_ptr,
                                     buffer->debug_id,
                                     buffer->transaction ? "active" : "finished");
-                       binder_free_buf(proc, thread, buffer);
+                       binder_free_buf(proc, thread, buffer, false);
                        break;
                }
 
@@ -4108,7 +4108,7 @@ retry:
                        buffer->transaction = NULL;
                        binder_cleanup_transaction(t, "fd fixups failed",
                                                   BR_FAILED_REPLY);
-                       binder_free_buf(proc, thread, buffer);
+                       binder_free_buf(proc, thread, buffer, true);
                        binder_debug(BINDER_DEBUG_FAILED_TRANSACTION,
                                     "%d:%d %stransaction %d fd fixups failed %d/%d, line %d\n",
                                     proc->pid, thread->pid,