[PATCH 5.8 193/633] binder: Remove bogus warning on failed same-process transaction

Greg Kroah-Hartman
2020-10-27T15:00:42Z

From: Jann Horn <jannh@google.com>

[ Upstream commit e8b8ae7ce32e17a5c29f0289e9e2a39c7dcaa1b8 ]

While binder transactions with the same binder_proc as sender and recipient
are forbidden, transactions with the same task_struct as sender and
recipient are possible (even though currently there is a weird check in
binder_transaction() that rejects them in the target==0 case).
Therefore, task_struct identities can't be used to distinguish whether
the caller is running in the context of the sender or the recipient.

Since I see no easy way to make this WARN_ON() useful and correct, let's
just remove it.

Fixes: 44d8047f1d87 ("binder: use standard functions to allocate fds")
Reported-by: syzbot+e113a0b970b7b3f394ba@syzkaller.appspotmail.com
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20200806165359.2381483-1-jannh@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/android/binder.c | 2 --
1 file changed, 2 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index af85d37aef680..adab46ca5dff7 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2324,8 +2324,6 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
* file is done when the transaction is torn
* down.
*/
- WARN_ON(failed_at &&
- proc->tsk == current->group_leader);
} break;
case BINDER_TYPE_PTR:
/*
--
2.25.1