From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-of-o52.zoho.com (sender4-of-o52.zoho.com [136.143.188.52]) (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 0A18E3FA5FC; Mon, 11 May 2026 13:58:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.52 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778507888; cv=pass; b=nLs2TrDf0RZ/E2BZ1VsZv2WxLUNCnVLt7OMlaOKD8nfsYxajx64rkXV3fchc7JK6uaezRT3j0Xp7ftQkQEiw11tlLNyUayaeEbv3a04brnfCI5MQGayEmXJowwv0RjV6/vQ+5Jt7qmmh2EecNhpBchC6wRCYnM1M9lXNMOoqLOA= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778507888; c=relaxed/simple; bh=Jcet8KyEkYiGBBVzYuhoikSoMWX60iw/0P0kcVi0sQw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BqAsmWbr52gOwJsga9+sxXZOPJqiRe1P1bHB/nKDYl3k7FIJC2iiSOWyYn2JU9vJ1tVwsNo/VitssTQOPd7q2krKbB/C9kki0RL0iyHTxwG1/ectnDHt2d7CTlipeGhSwZf4/+ZG8Dg7AyClK3oD3n9x6itqAN0WfTJgcANTpBQ= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=anirudhrb.com; spf=pass smtp.mailfrom=anirudhrb.com; dkim=pass (1024-bit key) header.d=anirudhrb.com header.i=anirudh@anirudhrb.com header.b=Nl1D/aFa; arc=pass smtp.client-ip=136.143.188.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=anirudhrb.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=anirudhrb.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=anirudhrb.com header.i=anirudh@anirudhrb.com header.b="Nl1D/aFa" ARC-Seal: i=1; a=rsa-sha256; t=1778507872; cv=none; d=zohomail.com; s=zohoarc; b=Bu8tC1HUXmpfyGk7mU+DHIMsuSjxWwssFDVXJrfMxnGRIrILotkQzYvsojF4wui0G9AGumalf1LYjviJw8iq1J2Ys2m1+FYX401UfCbyVLXC0cRxLK/NXv76/Q9eKFMNQP7BodmERXzaJmGhHEgDvh83C38LPPknFJzjl3p/kj0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1778507872; h=Content-Type:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=548LBP5jmiXtlRUysLGtYQXqCB1ATh62gSExfU6lrXQ=; b=oIa6zdP0TGkzvd+2cO4sRRTQVN1ehxacg4U1NcmlNJMmJeXMgwAZ41Kz+LIjZBJ5mu+CHPzYnGbpDSAT0y3LIH2CVtyXZDdG2wwMptUIF4D3lyQcapmlI8qPM4ew9IRTIxW7NSTwabs6gXL7GU/37uts59D8EWOhrBw34rN3Li0= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=anirudhrb.com; spf=pass smtp.mailfrom=anirudh@anirudhrb.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1778507872; s=zoho; d=anirudhrb.com; i=anirudh@anirudhrb.com; h=Date:Date:From:From:To:To:Cc:Cc:Subject:Subject:Message-ID:References:MIME-Version:Content-Type:In-Reply-To:Message-Id:Reply-To; bh=548LBP5jmiXtlRUysLGtYQXqCB1ATh62gSExfU6lrXQ=; b=Nl1D/aFazJIgy8e3N4g63oCwrX52+gzyHU7mo4AqpybBG8HQh7zUgttkhgAyQeCg yRl2+0xtgZe4z57Gl9Fcldl+W/DcwOXL2iYc9JCcxqcW1RPv7njeQvfXcViMCvpTo2V Dy+iUXeu5xcJlUIkCZxqqdgaPce/a8lPi0C4MF2M= Received: by mx.zohomail.com with SMTPS id 1778507868832481.82317095544613; Mon, 11 May 2026 06:57:48 -0700 (PDT) Date: Mon, 11 May 2026 13:57:42 +0000 From: Anirudh Rayabharam To: Stanislav Kinsburskii Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, longli@microsoft.com, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 03/18] mshv: Fix race in mshv_irqfd_deassign Message-ID: <20260511-musical-discerning-stoat-cbacce@anirudhrb> References: <177816592843.21765.4364464279247150355.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net> <177816859556.21765.6200058614819106223.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net> Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <177816859556.21765.6200058614819106223.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net> X-ZohoMailClient: External On Thu, May 07, 2026 at 03:43:15PM +0000, Stanislav Kinsburskii wrote: > mshv_irqfd_deactivate() and the hlist traversal of pt_irqfds_list > require pt->pt_irqfds_lock to be held, but mshv_irqfd_deassign() > omits it. This races with the EPOLLHUP path in mshv_irqfd_wakeup(), > which does take the lock before calling mshv_irqfd_deactivate(). > > Additionally, mshv_irqfd_deactivate() uses hlist_del() which poisons > the node pointers rather than resetting them. Since > mshv_irqfd_is_active() relies on hlist_unhashed() (checks pprev == > NULL), a poisoned node still appears active. If a concurrent path calls > mshv_irqfd_deactivate() again on the same irqfd, the guard fails to > prevent a double hlist_del() on poisoned pointers. > > Fix both issues: > - Add the missing spin_lock_irq/spin_unlock_irq around the list > traversal in mshv_irqfd_deassign(), matching mshv_irqfd_release(). > - Use hlist_del_init() instead of hlist_del() so the node is properly > marked as unhashed after removal, making the is_active guard reliable. > > Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") > Signed-off-by: Stanislav Kinsburskii > --- > drivers/hv/mshv_eventfd.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) Reviewed-by: Anirudh Rayabharam (Microsoft)