From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qt1-f171.google.com (mail-qt1-f171.google.com [209.85.160.171]) (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 7E3E7355055 for ; Thu, 24 Sep 2026 18:00:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790272827; cv=none; b=N7X5DVKML4ZnqrXcXXng2MiA/WqWMo+MdQran+hmOhql1qlDIpJbEdVa4kS0D4e+espkDaYMoAvuKh4W4LI/QeCgs0zYiXmveMswJguv8CbtmqJRdCLSzYgm9TT2o1bOliSfBdMWIbc3Q9tfCKiURsRUokqp+6O7uMAKTrSskL4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790272827; c=relaxed/simple; bh=dIEo2BWot8KMA7bFyxIXMBMINiO703u3CNAgbTnUo2E=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Jm7e4sPpr8fg+S75g8VA03Sb/RcoDO+CYUcF3eRqfdKriX6XhUSEcalCxhuMDpVY1FWn2TrOgRG6LVmmzDGQJ4SC2LUHiEjKcRbx8qPh9XeERjwvrdywWeHZiTNeErJ1jRZNc0B2epQsm/J3+cpA91HjeeWVXHD5azm46j6P4Qk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=gourry.net; spf=pass smtp.mailfrom=gourry.net; dkim=pass (2048-bit key) header.d=gourry.net header.i=@gourry.net header.b=qNcW8nj0; arc=none smtp.client-ip=209.85.160.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=gourry.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gourry.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gourry.net header.i=@gourry.net header.b="qNcW8nj0" Received: by mail-qt1-f171.google.com with SMTP id d75a77b69052e-52fa9c055b5so11364491cf.1 for ; Thu, 24 Sep 2026 11:00:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gourry.net; s=google; t=1790272822; x=1790877622; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=yIrEACM/1hk8RvSSdnwytl7iIy1+VcppA4PP9Tt2BDk=; b=qNcW8nj0/pDdjrHX+ELCleXyhNSH46+yVTvIwKXf0KEsO2lrNq/+t7BLtAJv/5kwUi 2AQLV5DG6nqODb54KYJ2Hhy8HyGJBZMXduXpgQLzeebEeIcn11k5EsbWxNYcGPXBaT1+ /qweihLG7noAHfK+Zx5EEGn0ruWcXq/Gj/S2WSYYG/9cAsBnCCVbDo0GQ6tr6T6jIO6M OeOdtj4ZPY+H89quivLjIZrF0JngYycSDR0/nPJVKUYp/eeTnJbocj21+VpbAezcSeJb 3sQPtmZy9+wwtqCXvsR5dE5N64+9dWM26DJ4nK/0tsdNaizI0KONqxKZScMTirDGCpdM wpaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790272822; x=1790877622; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=yIrEACM/1hk8RvSSdnwytl7iIy1+VcppA4PP9Tt2BDk=; b=VywJzimhAgoe4OqhGRCwoD8OOj7x9cB8ZVh+QEc34ctkHbl+HdI0qt3Og+fsiSDAvk u5+uycjjPwocabxlX2KxIbJHHb6SvqqiwQ7T46RwOOxndKjQa2hcFxM9WUWLv/hk0Arj U5EGi+THTKhhT3F9BTnRXzoJRvD1NP5dUCXFQLK1UKZXvu92eUSluAUSyLGjqv8azCaF RSw9aUyAutbwMVWlgrZV7gjx1GSEl28s9o6mha4t8rO01khamZClmCFPGBdHOQdPJhLC mww6QwuhSZlGVeMVOM8aDKGn7++xDk1QDX9kZGZL1CBZK+C9cWuEslsWwTbwLQIubEts n4jw== X-Forwarded-Encrypted: i=1; AKwUvBwTypGEyAzC+NwJUyncsjRGkyTo06keWoJJ76n35V7YI/NqFdUGLslNjGr6H1dGeRIUHTW8DsXPotndCCDb@vger.kernel.org X-Gm-Message-State: AFuF++lpA/ElMBbLksFhyRWyp+06j/mnfvOz6FGzj2LW2TPRskNFvDsY 6eOdj/mtAUPc3vLIbSA9Fy3joQeEgMeoeWiZsYJgFjTUmPOzCbZrwnQAuILfSylxLJU= X-Gm-Gg: AYBFou3KjmcyVThvWQkJ+jGJfPMLGIIqMybe+McsHESDv4fOv2kPjLlruaDXz2qr6Bp qbZvfDEuEEcpYeIEh5FUKoFF1+CUzMQV5sQ5RVSJ30c1TLJMqL1CFQrjmvha6NZr9Ns8vXjgVTq leuwR8bXbm2AiVzP/hhhyCEuvI54AZhPHl48ufcEts4TfouYas7QZHuGLEanYYOEdKxUgV64fCU AKYnSjH6GdZehHIUlXZ4hUBoYUKoKnUFKBxO++fUl6ucbOtHtvshGAhFuhZdI2/omV51oei7jca 8u2EH3+CsgRxcJF0a7t2wvSSvGvQ0Tk6G2wmHNHrjwKhGyJCCuL/aMU8t9eBtTepGH1YZINuA1N Fjk1ryoV39xnhL4QErcd8IStkAu3ACChDMUkAPEnZRYJC52bMAZOjPHOoWoyI56AtbQOCnoTNM3 1rS2OBfU4B63xHaMJmNljQCyQOm1+F5qyYIfQWSLtDsywLN/hH1yWSWoMxQJjVBsM+IMLkccT4L r1tmXFRHj85bFRo2fCmJzw5+bmJgpzHChTX43+1NJhJWZ8MVpwWXec= X-Received: by 2002:ac8:5a46:0:b0:530:e682:87c with SMTP id d75a77b69052e-5330b6df434mr78501cf.33.1790272821894; Thu, 24 Sep 2026 11:00:21 -0700 (PDT) Received: from gourry-fedora-PF4VCD3F (pool-173-79-60-52.washdc.fios.verizon.net. [173.79.60.52]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-532eb38d347sm47450101cf.25.2026.09.24.11.00.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Sep 2026 11:00:21 -0700 (PDT) Date: Thu, 24 Sep 2026 14:00:18 -0400 From: Gregory Price To: "Lorenzo Stoakes (ARM)" Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-usb@vger.kernel.org, linux-rdma@vger.kernel.org, selinux@vger.kernel.org, linux-sound@vger.kernel.org, bpf@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, fuse-devel@lists.linux.dev Subject: Re: [PATCH v3 05/40] mm/vma: ensure mmap_prepare doesn't set actions on a mergeable vma Message-ID: References: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@kernel.org> <20260917-b4-mmap-prepare-vma-flag-sanify-v3-5-4583d8a23bca@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@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: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-5-4583d8a23bca@kernel.org> On Thu, Sep 17, 2026 at 05:22:14PM +0100, Lorenzo Stoakes (ARM) wrote: > When a user requests an mmap_action be performed in mmap_prepare, this > involves populating the VMA range with data. > > However, if the VMA is mergeable, it might then mistakenly be merged with > another VMA without having populated the range. > > Every mmap action currently available sets VMA flags such that the VMA > cannot be merged. > > However, to ensure that no future mmap action falls foul of this, assert > that this is the case upon mmap_prepare validation. > > Signed-off-by: Lorenzo Stoakes (ARM) > --- > mm/vma.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/mm/vma.c b/mm/vma.c > index d6ed10cefc8f..62f2ce1ad5a1 100644 > --- a/mm/vma.c > +++ b/mm/vma.c > @@ -2809,6 +2809,15 @@ static int mmap_validate(unsigned long prev_start, unsigned long prev_end, > int mmap_prepare_validate(const struct vm_area_desc *prev_desc, > const struct vm_area_desc *desc) > { > + /* > + * It is not valid to execute mmap actions for VMAs which can be merged, > + * as any such merge would leave portions of the mapping incorrectly > + * unmapped. > + */ > + if (vma_flags_can_merge(&desc->vma_flags) && > + WARN_ON_ONCE(desc->action.type != MMAP_NOTHING)) > + return -EINVAL; > + If you wanted to make this unit-testable, you could pull it out into a separate function: static bool mmap_action_is_valid(const struct vm_area_desc *desc) { return desc->action.type == MMAP_NOTHING || !vma_flags_can_merge(&desc->vma_flags); } then write: if (WARN_ON_ONCE(!mmap_action_is_valid(desc))) return -EINVAL; And you can write a unit test directly against mmap_action_is_valid otherwise Reviewed-by: Gregory Price (Meta)