From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 5B7F4645 for ; Thu, 28 Aug 2025 00:16:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756340199; cv=none; b=ZZLWI5onByEgs5DstEvDvLPI6I9Hr2CaeZa3rDnZjdbCRI/zFbpsg+vv0e9Y1Uq5BlBEvCp11DWPDerB/DRuGiEI7P/A6d+NN6cmAzmLv2h6ivfINQhIbA5PM+p2PuLf+mvOyDbCC2U/pDZ/EViZwWfQj5+YYL17bouBK5XYpso= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756340199; c=relaxed/simple; bh=DRQULrR+FB4VYruNOuA3H9WZd2yskdckg89UGJxtXNI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=h+GRyYHWM8jNjpMT/jppSoWrkzS3acfMRRdt7xP5+FvrWMR42D4yCzP5BFtTvE/MjWyYfkRM74MwWwayEirFijS76htaK3iJdK0I9HNhJRM1lH1Gp6DgVDeJaPfL0vWsvQH3NwOB9hPJa3jzfcviZ+Iy3Mgn/kyCmaEo5vpzF64= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=xGKBFOaE; arc=none smtp.client-ip=209.85.214.201 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--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="xGKBFOaE" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2461c537540so4778115ad.0 for ; Wed, 27 Aug 2025 17:16:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1756340197; x=1756944997; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=gN/JTBUQGojSDyUMvLZLw43SnOlQ5Fr1I8L6kd4ekdw=; b=xGKBFOaErHGPI+jd+8sUXO1g/7PTjCoW7j/fS9gLGoC+YZZdPCq9apo7Fv9m+v1DAT z8p+6OOqXY5mpiEjO0neHwD4vWQiKKxDIt3omaj4wF0NA493KLmDYKJJDDid/69m7CxH e4gwk6vm6PrZG0T7cp40skGw9ah9KIhQrPLKeb51jX4o3r/R/WbDO4L6rzhVMNN17p/H 1ERDLGiprqX6k9FmWJKM6x81CGdo7WuBsDEip4OAkDqeXH2UrihYUV0WVxLyD0yH1Y9X LaIb5AJAQtw33HyxbBIoJdXwmPFTUnxw72MrEsijSlsAwq8oCioLRUi4UITAOsMP2f1E EuSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756340197; x=1756944997; h=content-transfer-encoding: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=gN/JTBUQGojSDyUMvLZLw43SnOlQ5Fr1I8L6kd4ekdw=; b=QVUvDRtFkiN/vU0/uo3R3OuJ+5AqFlXo6X6zRKPVceYm5XSXuuXARkfLy3ZJfvJfeR bl8rOy6z3aLTDz9dnmKKxegdnP7W7sQadZCuAu8lVKP9qIeztOB2mCr7/0rpqOn65qmX 4U7duqffFm87lTb0od9P+vXueCpee+OSkGartjwgiGksAQ41Fu6gm1QOfqzpWCoACsFo MgyMmtGKLI9z1WqPD0b+sRSblu4tMUa7o3EVstNBqQ32uIXe2XmJWHZCYFTy8ULHYop/ JfqSyPm050SNPRj91kcxs2xG7rFB5D+eR4sKPOQtPks79VTW1xmolbZofUGAs0wSvE3D 2bTQ== X-Forwarded-Encrypted: i=1; AJvYcCVWk8WYADP6SmrM8D4ycLtKvNDmA6CuOXKUBuAHo2V5CDB4lFUL762LOAIlPODUCOiy4yFMzFTWp+hJkwc=@vger.kernel.org X-Gm-Message-State: AOJu0Yxek1RYmypU5iNjXOkLr6TjbQTQKZNKp132tPdoiRB4jGrTgf48 pla0PY8EXreZcnJUOfyvfBD8L7JIETZBJA4e69Fx2nA8yhAHQ3MNSeh3600qQhZE8owrTsd4Qvu WhxfzYA== X-Google-Smtp-Source: AGHT+IEeaZ+vZ1azz2+/JevayRHNowIgRsI1vZgWUZcfRT1k7jmZ4DcsJTv92NsfT4neFY+yGzMEa3j4/Ro= X-Received: from pjxx6.prod.google.com ([2002:a17:90b:58c6:b0:324:ed49:6c92]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:94e:b0:246:ae6e:e5db with SMTP id d9443c01a7336-246ae6ee847mr198532435ad.42.1756340196775; Wed, 27 Aug 2025 17:16:36 -0700 (PDT) Date: Wed, 27 Aug 2025 17:16:35 -0700 In-Reply-To: <20250827201059.EmmdDFB_@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250827194107.4142164-1-seanjc@google.com> <20250827201059.EmmdDFB_@linutronix.de> Message-ID: Subject: Re: [PATCH v2 0/3] vhost_task: Fix a bug where KVM wakes an exited task From: Sean Christopherson To: Sebastian Andrzej Siewior Cc: Paolo Bonzini , "Michael S. Tsirkin" , Jason Wang , kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Wed, Aug 27, 2025, Sebastian Andrzej Siewior wrote: > On 2025-08-27 12:41:04 [-0700], Sean Christopherson wrote: > > Michael, >=20 > Sean, >=20 > would the bellow work by chance? It is a quick shot but it looks > symmetrical=E2=80=A6 Gah, sorry, I flagged your earlier mail and then forgot to circle back to i= t (for whatever reason, I didn't entirely grok what you were suggesting). > diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c > index bc738fa90c1d6..27107dcc1cbfe 100644 > --- a/kernel/vhost_task.c > +++ b/kernel/vhost_task.c > @@ -100,6 +100,7 @@ void vhost_task_stop(struct vhost_task *vtsk) > * freeing it below. > */ > wait_for_completion(&vtsk->exited); > + put_task_struct(vtsk->task); > kfree(vtsk); > } > EXPORT_SYMBOL_GPL(vhost_task_stop); > @@ -148,7 +149,7 @@ struct vhost_task *vhost_task_create(bool (*fn)(void = *), > return ERR_CAST(tsk); > } > =20 > - vtsk->task =3D tsk; > + vtsk->task =3D get_task_struct(tsk); > return vtsk; > } > EXPORT_SYMBOL_GPL(vhost_task_create); Nice! This fixes things too. Either solution works for me. Or maybe do b= oth? Attempting to wake a task that vhost_task knows has exited (is exiting?) is= a bit gross, but even with that hardening, guarding against UAF is very nice = to have too. Tested-by: Sean Christopherson