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 5B82E18E3F 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=1756340200; cv=none; b=iQGskhS2zXZuAA27OHJoSaVMsUCikEBNF2gMZGSU0Q0o0FNt5zz843pQuuXUVzCDio3j2cfBZbA/tzGm+3kuZxCsfQSzYt/8aQBe5oL/DFrnVEiAEmBMAEGCoh5VPXy8jVFS/3XYSXjpanQhLC7Cv7umUPh2b0FY9ZvmhdTMA94= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756340200; c=relaxed/simple; bh=DRQULrR+FB4VYruNOuA3H9WZd2yskdckg89UGJxtXNI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=nkNg5fPzCguieuOoI1JFtl8+lCcfXIUySrz8IqLASjkUcg0fumwwAfz1M+bj0C3Uu1QrtCEqwZNwCUhUWJ9mKtQUoAcrZBe5gxlS/4+YgoNJmFDZbIExkVhmsRYA7BTz074I3dJdRuIeYS0NZU1ki7XLj12IV2movaPM4GQHMJE= 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=UwvOPlJ5; 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="UwvOPlJ5" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2461c537540so4778105ad.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=lists.linux.dev; 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=UwvOPlJ5MRFGcHKk7llnIdBb6ye3pxzECZYTI4JNrq/aAXd39dtDFBw4VJu9qfJmDZ M+WjzvVDZrqc2dpkg4MBNoO5OissUW6ToRoA4s+0edFsTfDPgrg7wgDyxZR+sNpccowW NPYS5QjdNFuoD7GKcqZA0AvvdcAVLszRXF0d52ct9gypT6Ld3co/4VFTca9bkj9NREv6 YZaZyakJNck3RMrIz5FtXEhVJOmr8L8f9ag6OlSe1N1+W3iQkTffSNiSx7dqPmG2HdOL 2A8iyYGRctVTF3HEdZakI3wWHLzNmQl9DSBgQ+7MM9Izk6OsosHfdpMsdWDAIyYNGF+8 af1w== 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=l3lphKZtdGa2sop/fbvDbtJRccrytgaEux4CnNRFFCFG7FHm3NnfokCncbGIp9cKp5 TZCnpuYGWEMHDRcNo3oTGiicrQLJQAPbjJDHCKC08H8EK+mYjBcp5hnrb6GT2QI+4fE8 qy28LKKuFN1739yrHW1SV5CbQf0qRETOfqFMM+IpYPuqu8FzEmUhlI2Aawq86KqTW55Z JSFC/TkRFWXwTflAqX7ah6omr/g10pcnRd4Xa7cIbGWPDNkqUsnDNPmpTX3GEfZZHu0U NH+aMYX8bjhA0rVZ2LU9+NnxHEoZhOCtnzTjYJUVPS+2ru3VZkTwvoYJbrCMkFePZwZz Jgcg== X-Forwarded-Encrypted: i=1; AJvYcCXbt/CEV0bk+l7SOmZhwHtssB092X3twl92yhsD7IxPzTaAK5Dx7unWl7RGz/PUrerBIJRBrWrYq4A2CFYtFw==@lists.linux.dev X-Gm-Message-State: AOJu0YzO6gsk751RaBlE2SqQzGclOO0gNc1wEHDKF0mTJ/J8mguNRv1S iSQjn+6yXMs8+O17hSf7fNDPj3HW6o+BKAqF4DE1hd/DRHEUK+IrPXpxinlUeQtXF3CSsjwFbrf /sZfpmw== 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: virtualization@lists.linux.dev 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