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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+e113a0b970b7b3f394ba@syzkaller.appspotmail.com,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Todd Kjos <tkjos@google.com>, Jann Horn <jannh@google.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.8 193/633] binder: Remove bogus warning on failed same-process transaction
Date:   Tue, 27 Oct 2020 14:48:56 +0100
Message-Id: <20201027135531.729146503@linuxfoundation.org>
In-Reply-To: <20201027135522.655719020@linuxfoundation.org>
References: <20201027135522.655719020@linuxfoundation.org>
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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