From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0B59233F8DA; Thu, 15 Jan 2026 16:59:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768496381; cv=none; b=b3qH3lX3Leaa1rkUtwO/pZRl8Sg6owdwc+XpvBerqUA3e/3c+FVHamFAuOgPQqXWdP2uREnlmST7p/5xX7U0SA+FO2VtkPlozjQYpX89pi4bckAk4Np1GjFTDtrnadyQ/+Z+7ZoWuzBieK4+zW4u8r/unJ387m9TecLRe25UzsY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768496381; c=relaxed/simple; bh=KAi3myD4Va9ohcwOn/MdIlQYdTXAEkFCxaxGUKDlIBI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=L9Zi2ja1Qe41vhuYE4naG1QMZmShJNfOd77xJd76YyMIsrkst0HbJ1kMhbX0Q+rcMYBOksFxZIpQn3WerzOlgAr6TjqoPdGjC2h6dnv1WV4N1NYqhbjN8ZggezqqharZIQkJfT60Vi/bSjX4bBZGDskKtGy+FzBkkAHAb/nby/s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=YJIJDc1x; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="YJIJDc1x" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F4A2C116D0; Thu, 15 Jan 2026 16:59:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1768496380; bh=KAi3myD4Va9ohcwOn/MdIlQYdTXAEkFCxaxGUKDlIBI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YJIJDc1xlCJASAvucZ8j6lbqJA6AdkplP+gST/fjiiWKYEB0T7SCIecWYnbiP4RY9 gNI9HTFj0O02fwciAKC6XIDkTb4wltH4qI20TwUoZbeGLq899hIT49Hsp1jRAuxbLu 0lihxE0KXnwMa8bDunaSi+hNIjdtbNOKV/4JyeOw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot , Tetsuo Handa , Oleksij Rempel , Marc Kleine-Budde , Sasha Levin Subject: [PATCH 6.18 174/181] can: j1939: make j1939_session_activate() fail if device is no longer registered Date: Thu, 15 Jan 2026 17:48:31 +0100 Message-ID: <20260115164208.596142601@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260115164202.305475649@linuxfoundation.org> References: <20260115164202.305475649@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tetsuo Handa [ Upstream commit 5d5602236f5db19e8b337a2cd87a90ace5ea776d ] syzbot is still reporting unregister_netdevice: waiting for vcan0 to become free. Usage count = 2 even after commit 93a27b5891b8 ("can: j1939: add missing calls in NETDEV_UNREGISTER notification handler") was added. A debug printk() patch found that j1939_session_activate() can succeed even after j1939_cancel_active_session() from j1939_netdev_notify(NETDEV_UNREGISTER) has completed. Since j1939_cancel_active_session() is processed with the session list lock held, checking ndev->reg_state in j1939_session_activate() with the session list lock held can reliably close the race window. Reported-by: syzbot Closes: https://syzkaller.appspot.com/bug?extid=881d65229ca4f9ae8c84 Signed-off-by: Tetsuo Handa Acked-by: Oleksij Rempel Link: https://patch.msgid.link/b9653191-d479-4c8b-8536-1326d028db5c@I-love.SAKURA.ne.jp Signed-off-by: Marc Kleine-Budde Signed-off-by: Sasha Levin --- net/can/j1939/transport.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index fbf5c8001c9df..613a911dda100 100644 --- a/net/can/j1939/transport.c +++ b/net/can/j1939/transport.c @@ -1567,6 +1567,8 @@ int j1939_session_activate(struct j1939_session *session) if (active) { j1939_session_put(active); ret = -EAGAIN; + } else if (priv->ndev->reg_state != NETREG_REGISTERED) { + ret = -ENODEV; } else { WARN_ON_ONCE(session->state != J1939_SESSION_NEW); list_add_tail(&session->active_session_list_entry, -- 2.51.0