From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3110BC98318 for ; Thu, 24 Sep 2026 15:36:44 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C269C10F680; Thu, 24 Sep 2026 15:36:43 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="gsARZPL+"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6EBF910F66C; Thu, 24 Sep 2026 15:36:42 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id E78F7601DE; Thu, 24 Sep 2026 15:36:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B2891F000FF; Thu, 24 Sep 2026 15:36:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790264201; bh=GVD/OkLLNkpzpvvBUDDvU2PFPsttaitYj94/0tnnw2o=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=gsARZPL+APvFcCEgHdnuC4a9QeLn0KKhWoY/tMr+H5EUMRE4Snxxpv++yvdCy2T5j 1676IJ4mBGTIyh2vAeVpTId7yi2VTJMkSwUA8sNfJ45VNUV9vkGaS1+IBoFhJ9fHrp /9+hECI9SXKJm2rsdJJTVt4EreFvedJwRz1+F2B3XBAmlQbMLOsfQ9i0t9WSXgSB66 bftBj/6e2tFNzsfIYV+xMTzZWu7DTpc3YD5jWanrnD2KFkBLa87JdTJVQAnWlumYyG Vi+RUHP/FP7G6lwZyxPP5rd8lSWq07lI8/ZJWWA+DQbapNcULb8AH8XrIHdx78ZrC9 PnBj7XsHvZyDA== From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 1/1] drm/i915/gmbus: Add bit-banging debugfs control To: "Naladala Ramanaidu" Cc: intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org In-Reply-To: <20260924152812.439986-2-ramanaidu.naladala@intel.com> References: <20260924152812.439986-1-ramanaidu.naladala@intel.com> <20260924152812.439986-2-ramanaidu.naladala@intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 24 Sep 2026 15:36:40 +0000 Message-Id: <20260924153641.6B2891F000FF@smtp.kernel.org> X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [Medium] drm/i915: race in debugfs write causes force_bit refcount corrup= tion -- commit dbe416d20c046e80d3b0b6e516a640339bbbd1e9 Author: Naladala Ramanaidu drm/i915/gmbus: Add bit-banging debugfs control This commit adds a connector debugfs interface to enable or disable I2C bit-banging for Intel GMBUS adapters. > diff --git a/drivers/gpu/drm/i915/display/intel_gmbus.c b/drivers/gpu/drm= /i915/display/intel_gmbus.c > index 60a70dea5d856..38d6d11483994 100644 > --- a/drivers/gpu/drm/i915/display/intel_gmbus.c > +++ b/drivers/gpu/drm/i915/display/intel_gmbus.c [ ... ] > +static ssize_t intel_force_bit_banging_write(struct file *file, > + const char __user *ubuf, > + size_t len, loff_t *offp) > +{ > + struct seq_file *m =3D file->private_data; > + struct intel_connector *connector =3D m->private; > + bool force_bit_banging; > + int ret; > + > + ret =3D kstrtobool_from_user(ubuf, len, &force_bit_banging); > + if (ret) > + return ret; > + > + if (force_bit_banging !=3D connector->force_bit_banging) { > + intel_gmbus_force_bit(connector->base.ddc, force_bit_banging); > + connector->force_bit_banging =3D force_bit_banging; > + } [Severity: Medium] Is this state transition safe against concurrent debugfs writes? Since this read-modify-write block on connector->force_bit_banging is not protected by any locks, multiple threads concurrently writing to the intel_force_bit_banging debugfs file could trigger multiple calls to intel_gmbus_force_bit() for the same state change. Looking at intel_gmbus_force_bit(), it manages bus->force_bit as a reference count: drivers/gpu/drm/i915/display/intel_gmbus.c:intel_gmbus_force_bit() { ... mutex_lock(&display->gmbus.mutex); bus->force_bit +=3D force_bit ? 1 : -1; ... } Could unbalanced calls resulting from a race here cause the refcount to underflow or leak, permanently forcing bit-banging mode for the adapter? > + *offp +=3D len; > + > + return len; > +} [ ... ] --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260924152812.4399= 86-1-ramanaidu.naladala@intel.com?part=3D1