linux-kernel - [PATCH 4.19 103/113] binder: prevent transactions to context manager from its own process.

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Date:   Mon, 29 Jul 2019 21:23:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+8b3c354d33c4ac78bfad@...kaller.appspotmail.com,
        Hridya Valsaraju <hridya@...gle.com>,
        Todd Kjos <tkjos@...gle.com>
Subject: [PATCH 4.19 103/113] binder: prevent transactions to context manager from its own process.

From: Hridya Valsaraju <hridya@...gle.com>

commit 49ed96943a8e0c62cc5a9b0a6cfc88be87d1fcec upstream.

Currently, a transaction to context manager from its own process
is prevented by checking if its binder_proc struct is the same as
that of the sender. However, this would not catch cases where the
process opens the binder device again and uses the new fd to send
a transaction to the context manager.

Reported-by: syzbot+8b3c354d33c4ac78bfad@...kaller.appspotmail.com
Signed-off-by: Hridya Valsaraju <hridya@...gle.com>
Acked-by: Todd Kjos <tkjos@...gle.com>
Cc: stable <stable@...r.kernel.org>
Link: https://lore.kernel.org/r/20190715191804.112933-1-hridya@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/android/binder.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2838,7 +2838,7 @@ static void binder_transaction(struct bi
 			else
 				return_error = BR_DEAD_REPLY;
 			mutex_unlock(&context->context_mgr_node_lock);
-			if (target_node && target_proc == proc) {
+			if (target_node && target_proc->pid == proc->pid) {
 				binder_user_error("%d:%d got transaction to context manager from process owning it\n",
 						  proc->pid, thread->pid);
 				return_error = BR_FAILED_REPLY;