From patchwork Tue Jun 17 05:07:12 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuen-Han Tsai X-Patchwork-Id: 897949 Received: from mail-lj1-f201.google.com (mail-lj1-f201.google.com [209.85.208.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DA98F23B625 for ; Tue, 17 Jun 2025 05:08:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750136938; cv=none; b=iwEcJxVK7bUNlxY8rcZ1ZubWhI9mRPXTt2GYzlTdUZR/r7yWmmov0Cg8or7Wl3xQzStsDjsSRdlAk3wp8A2nDMo/syIFLXDh3UnAmirksaOt4QR1N9T3MHb69v5nr2QZ0LwEjZwfF9wgxNoqL4rcqnAmiK2EJdCbdf/Pmz9kgWo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750136938; c=relaxed/simple; bh=YoOKZWDe3bgJ0VNg0eea3oWFhS1QY5GJUZB2g124DaM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=NRe9ib/opbjPuPvvU19Pa3YCDoWRraZRRPtN1swlYStiQjDK7zHGdin9RKOLFIWuP5VxcwFNSfYs8dxsJLFa5qxx8YRtjoVip/rcnMkUB0CKR/G9q9FU3472tmU/60WWPCskns7aHbsSa51Te3SLSOGX7pkycqwLXSWV2P6yuZY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--khtsai.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=z2Nd4Hg5; arc=none smtp.client-ip=209.85.208.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--khtsai.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="z2Nd4Hg5" Received: by mail-lj1-f201.google.com with SMTP id 38308e7fff4ca-32b2de6033bso31743131fa.1 for ; Mon, 16 Jun 2025 22:08:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1750136934; x=1750741734; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=1f3cBdI8xhkfW1PldN25AHnH1CARokeiI9s7jI03ZKc=; b=z2Nd4Hg5HqvusKgpB32GJ1XMbAfQqFY5ncKCgWb3l7CqCyVvlXnKZX8Lp+1Z8M7FtO 0fqXzxfT9iZ/0j+b+kSe8CVleph3y4kUTClpT2BleMkDc5Cey9Fn2rLRjyG4yMJMAlBP Vi/Ymt/1q8z/7WdBke5bioCNP2Po5/zpaCKY6Z/WnLrtu7pwF7enTGE2tf8ZsVXXdupc /T2ruzjPW1FGIQfemPWzr35xaqvoyd/Np4z8DFmlaOlEWGIdbP14hGMAwOgs5dQT+/Fx j/l8cmhBXtByPbrcoOf3kDE8nRmPrO9K9v0HBXNMIuprIbofklnu1QrY520dCUcXZKFM cmnA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750136934; x=1750741734; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=1f3cBdI8xhkfW1PldN25AHnH1CARokeiI9s7jI03ZKc=; b=Y86Q4EAVQngwtorX3yCcrpp5IC4UW/ehLHfCxNoWGGMIyMR4CAu9OFhN4psCc3knmB 8DB+ojht+EGjh1ch21SBlK+isN716bvpXcEEz93dnLE3UszNT+SGNpEyMF5HCGiamw2x ajJQTO5ouD7afJYOf63wwT7t1d5Qij0jZCDF1GT69xV+SLhoi8dnEhxbvg0oa2jLbMbL XvC7AXxrH7seYvBD3ZB3MzB8gr6QYp0XIij7PIIINf28C7zQdlCe5wL+eQDd4SeldtAm NwkYzWmzHD64QZJgeR201iBYApRJpKex2oZiexUEwQl/iZZC6c6S95Z+oQSTqkvZ9kZ4 Na2Q== X-Gm-Message-State: AOJu0YzSp0ihfYrLav3HkwBJEGpdcdg8acyT7L1k0XM50w1ZJXy4MLyF wr0uzqfu9DUgP8VtHjI6seUD3UgtIj1RWi9A5Nm7Au1jGDjOJWLUxFqhttme2l7olg9HidsFH0f a85bdFw== X-Google-Smtp-Source: AGHT+IFYSpjBdNE9GBi8neTP2Ze6oQSxzs3XDaNIiK3QW1FHbqEsFzdEHcQZ/oyym4KEV3rZRaUJ4kszYmQ= X-Received: from ljqj16.prod.google.com ([2002:a2e:a910:0:b0:32a:807c:a3a7]) (user=khtsai job=prod-delivery.src-stubby-dispatcher) by 2002:a05:651c:154b:b0:32b:4932:d5ad with SMTP id 38308e7fff4ca-32b49508ae0mr28534501fa.10.1750136933782; Mon, 16 Jun 2025 22:08:53 -0700 (PDT) Date: Tue, 17 Jun 2025 13:07:12 +0800 In-Reply-To: <20250617050844.1848232-1-khtsai@google.com> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250617050844.1848232-1-khtsai@google.com> X-Mailer: git-send-email 2.50.0.rc2.692.g299adb8693-goog Message-ID: <20250617050844.1848232-2-khtsai@google.com> Subject: [PATCH v2 2/2] usb: gadget: u_serial: Fix race condition in TTY wakeup From: Kuen-Han Tsai To: gregkh@linuxfoundation.org, prashanth.k@oss.qualcomm.com, khtsai@google.com, hulianqin@vivo.com, krzysztof.kozlowski@linaro.org, mwalle@kernel.org, jirislaby@kernel.org Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org A race condition occurs when gs_start_io() calls either gs_start_rx() or gs_start_tx(), as those functions briefly drop the port_lock for usb_ep_queue(). This allows gs_close() and gserial_disconnect() to clear port.tty and port_usb, respectively. Use the null-safe TTY Port helper function to wake up TTY. Example CPU1: CPU2: gserial_connect() // lock gs_close() // await lock gs_start_rx() // unlock usb_ep_queue() gs_close() // lock, reset port.tty and unlock gs_start_rx() // lock tty_wakeup() // NPE Fixes: 35f95fd7f234 ("TTY: usb/u_serial, use tty from tty_port") Cc: stable@vger.kernel.org Signed-off-by: Kuen-Han Tsai --- v2: - Move the example up to the changelog Traces: [ 51.494375][ T278] ttyGS1: shutdown [ 51.494817][ T269] android_work: sent uevent USB_STATE=DISCONNECTED [ 52.115792][ T1508] usb: [dm_bind] generic ttyGS1: super speed IN/ep1in OUT/ep1out [ 52.516288][ T1026] android_work: sent uevent USB_STATE=CONNECTED [ 52.551667][ T1533] gserial_connect: start ttyGS1 [ 52.565634][ T1533] [khtsai] enter gs_start_io, ttyGS1, port->port.tty=0000000046bd4060 [ 52.565671][ T1533] [khtsai] gs_start_rx, unlock port ttyGS1 [ 52.591552][ T1533] [khtsai] gs_start_rx, lock port ttyGS1 [ 52.619901][ T1533] [khtsai] gs_start_rx, unlock port ttyGS1 [ 52.638659][ T1325] [khtsai] gs_close, lock port ttyGS1 [ 52.656842][ T1325] gs_close: ttyGS1 (0000000046bd4060,00000000be9750a5) ... [ 52.683005][ T1325] [khtsai] gs_close, clear ttyGS1 [ 52.683007][ T1325] gs_close: ttyGS1 (0000000046bd4060,00000000be9750a5) done! [ 52.708643][ T1325] [khtsai] gs_close, unlock port ttyGS1 [ 52.747592][ T1533] [khtsai] gs_start_rx, lock port ttyGS1 [ 52.747616][ T1533] [khtsai] gs_start_io, ttyGS1, going to call tty_wakeup(), port->port.tty=0000000000000000 [ 52.747629][ T1533] Unable to handle kernel NULL pointer dereference at virtual address 00000000000001f8 --- drivers/usb/gadget/function/u_serial.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) -- 2.50.0.rc2.692.g299adb8693-goog diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index c043bdc30d8a..540dc5ab96fc 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -295,8 +295,8 @@ __acquires(&port->port_lock) break; } - if (do_tty_wake && port->port.tty) - tty_wakeup(port->port.tty); + if (do_tty_wake) + tty_port_tty_wakeup(&port->port); return status; } @@ -574,7 +574,7 @@ static int gs_start_io(struct gs_port *port) gs_start_tx(port); /* Unblock any pending writes into our circular buffer, in case * we didn't in gs_start_tx() */ - tty_wakeup(port->port.tty); + tty_port_tty_wakeup(&port->port); } else { /* Free reqs only if we are still connected */ if (port->port_usb) {