linux-kernel - [PATCH] binder: do not crash on bad transaction in binder_thread

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Message-ID: <20250331152515.113421-1-fisaksen@baylibre.com>
Date: Mon, 31 Mar 2025 17:24:14 +0200
From: Frode Isaksen <fisaksen@...libre.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 <brauner@...nel.org>,
	Carlos Llamas <cmllamas@...gle.com>,
	Suren Baghdasaryan <surenb@...gle.com>
Cc: Frode Isaksen <frode@...a.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] binder: do not crash on bad transaction in binder_thread_release()

From: Frode Isaksen <frode@...a.com>

Instead of calling BUG(), set the binder_thread to NULL,
as is done in other parts of the code.
Log if it is a bad transaction (other than in or out).
The BUG in binder_thread_release() was preceded by
these warning logs:
binder: 1198:1217 got reply transaction with bad transaction stack,
 transaction 49693 has target 1198:0
binder: 1198:1217 transaction failed 29201/-71, size 4-0 line 3065
...
binder: release 954:1333 transaction 49693 out, still active
...
binder: release 1198:1217 transaction 49693 out, still active
kernel BUG at drivers/android/binder.c:5070!

Signed-off-by: Frode Isaksen <frode@...a.com>
---
This bug was discovered, tested and fixed (no more crashes seen) on Meta Quest 3 device.

 drivers/android/binder.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 76052006bd87..c21d7806e42b 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -5302,7 +5302,8 @@ static int binder_thread_release(struct binder_proc *proc,
 			     "release %d:%d transaction %d %s, still active\n",
 			      proc->pid, thread->pid,
 			     t->debug_id,
-			     (t->to_thread == thread) ? "in" : "out");
+			     (t->to_thread == thread) ? "in" :
+			     (t->from == thread) ? "out" : "bad");
 
 		if (t->to_thread == thread) {
 			thread->proc->outstanding_txns--;
@@ -5317,7 +5318,7 @@ static int binder_thread_release(struct binder_proc *proc,
 			t->from = NULL;
 			t = t->from_parent;
 		} else
-			BUG();
+			t = NULL;
 		spin_unlock(&last_t->lock);
 		if (t)
 			spin_lock(&t->lock);
-- 
2.49.0