linux-kernel - [PATCH] binder: Remove bogus warning on failed same-process transaction

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Message-Id: <20200806165359.2381483-1-jannh@google.com>
Date:   Thu,  6 Aug 2020 18:53:59 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Arve Hjønnevåg" <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <christian@...uner.io>,
        Hridya Valsaraju <hridya@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: [PATCH] binder: Remove bogus warning on failed same-process transaction

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@...kaller.appspotmail.com
Signed-off-by: Jann Horn <jannh@...gle.com>
---
 drivers/android/binder.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index f936530a19b0..5b0376344dbe 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2344,8 +2344,6 @@ 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:
 			/*

base-commit: 47ec5303d73ea344e84f46660fff693c57641386
-- 
2.28.0.163.g6104cc2f0b6-goog