patch "binder: don't detect sender/target during buffer cleanup" added to char-misc-testing

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

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

to my char-misc git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-testing branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will be merged to the char-misc-next branch sometime soon,
after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.


From 32e9f56a96d8d0f23cb2aeb2a3cd18d40393e787 Mon Sep 17 00:00:00 2001
From: Todd Kjos <tkjos@google.com>
Date: Fri, 15 Oct 2021 16:38:11 -0700
Subject: binder: don't detect sender/target during buffer cleanup

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>
---
 drivers/android/binder.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 9edacc8b9768..fe4c3b49eec1 100644
--- 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.
 				 */
@@ -3185,6 +3184,7 @@ static void binder_transaction(struct binder_proc *proc,
  * 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.
@@ -3194,7 +3194,7 @@ static void binder_transaction(struct binder_proc *proc,
 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) {
@@ -3222,7 +3222,7 @@ 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);
 }
 
@@ -3424,7 +3424,7 @@ 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;
 		}
 
@@ -4117,7 +4117,7 @@ static int binder_thread_read(struct binder_proc *proc,
 			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,
-- 
2.33.1