linux-kernel - [v2] ANDROID: binder: prevent transactions into own process.

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Message-Id: <20180328091233.83914-1-maco@android.com>
Date:   Wed, 28 Mar 2018 11:12:33 +0200
From:   Martijn Coenen <maco@...roid.com>
To:     gregkh@...uxfoundation.org, john.stultz@...aro.org,
        tkjos@...gle.com, arve@...roid.com, amit.pundir@...aro.org
Cc:     linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
        maco@...gle.com, Martijn Coenen <maco@...roid.com>
Subject: [v2] ANDROID: binder: prevent transactions into own process.

This can't happen with normal nodes (because you can't get a ref
to a node you own), but it could happen with the context manager;
to make the behavior consistent with regular nodes, reject
transactions into the context manager by the process owning it.

Reported-by: syzbot+09e05aba06723a94d43d@...kaller.appspotmail.com
Signed-off-by: Martijn Coenen <maco@...roid.com>
---
Changed in v2:
   - Use target_proc directly to avoid dereference.

 drivers/android/binder.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 764b63a5aade..e578eee31589 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2839,6 +2839,14 @@ static void binder_transaction(struct binder_proc *proc,
 			else
 				return_error = BR_DEAD_REPLY;
 			mutex_unlock(&context->context_mgr_node_lock);
+			if (target_node && target_proc == proc) {
+				binder_user_error("%d:%d got transaction to context manager from process owning it\n",
+						  proc->pid, thread->pid);
+				return_error = BR_FAILED_REPLY;
+				return_error_param = -EINVAL;
+				return_error_line = __LINE__;
+				goto err_invalid_target_handle;
+			}
 		}
 		if (!target_node) {
 			/*
-- 
2.17.0.rc1.321.gba9d0f2565-goog