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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D348EB64DD for ; Thu, 27 Jul 2023 21:52:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BA47B6B0072; Thu, 27 Jul 2023 17:52:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B553D6B0074; Thu, 27 Jul 2023 17:52:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9F5476B0075; Thu, 27 Jul 2023 17:52:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 8C60A6B0072 for ; Thu, 27 Jul 2023 17:52:43 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 5D006A0230 for ; Thu, 27 Jul 2023 21:52:43 +0000 (UTC) X-FDA: 81058741806.05.070A0C7 Received: from mail-yb1-f171.google.com (mail-yb1-f171.google.com [209.85.219.171]) by imf26.hostedemail.com (Postfix) with ESMTP id 95D6D14000F for ; Thu, 27 Jul 2023 21:52:41 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=jXRZ7Kmj; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf26.hostedemail.com: domain of surenb@google.com designates 209.85.219.171 as permitted sender) smtp.mailfrom=surenb@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1690494761; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=4KPOtYqoOes1CwPA7Jr9Y4W2AOtCMCx1fJ4T2541xI4=; b=Ux+e4LkItf3+Ky821yK9uIxg/tJGfPzFnnHHom6zU2qMiz/36h/a4dACGNpB1vftc6ECcB Iqc9OZJANSjhJnoWgiszV6i4W9GSuUliXHqOGJqBr5Y4zfWkFWea+YIEtCDd6rK/RUc0vl sAlGnkCRRjfNTgWA/nJoBmTnl4JKQRQ= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=google.com header.s=20221208 header.b=jXRZ7Kmj; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf26.hostedemail.com: domain of surenb@google.com designates 209.85.219.171 as permitted sender) smtp.mailfrom=surenb@google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1690494761; a=rsa-sha256; cv=none; b=BSJacyPlBikCjlVTJ7HhGYL3vC9RWK73vqk0fTaoVgSwifBrt98o/yPadnER+EfyvoiLCC 4q2PkX5lbk1TiDFPlgFXGt5Kl4ilBgxbWb47U72yeUU8UxuV1YFYQ7vLQngWAMoUFfrPCD xKLawfs0J+RvpiLHj2vdQGMxc8uXCGY= Received: by mail-yb1-f171.google.com with SMTP id 3f1490d57ef6-c5f98fc4237so1277793276.2 for ; Thu, 27 Jul 2023 14:52:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1690494760; x=1691099560; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=4KPOtYqoOes1CwPA7Jr9Y4W2AOtCMCx1fJ4T2541xI4=; b=jXRZ7KmjH+Cq+ZbNqpwHiH19bHmNc0OqzIL99k8dYjmCAriZEMM4GIedx5Gx59m9po N1uxwosjUlYFte8gwy9D4899dUV9CRZ1QgAnWLYXjdvOiZLC+Lp+mkQLOUxFemL3DNGO HqkKqxZos4jyrP9XafK+sQhavS7+FVtz9WX103LkbYPB9VN4H0QUinLu+F/UD2mN6pp7 ecIwU08PWKmaTB/zAUrN0hMhe6DdmngiqIp3E6W1z//C4pohRKjQkBFdIzJaa+yLX4/N ASGe7bsL9a6aAryuxBc/Fr04nvbcyWj/97W5VSA0MrVll+ryz0FFh4lwhEyFXyr64HVN Y/ew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690494760; x=1691099560; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=4KPOtYqoOes1CwPA7Jr9Y4W2AOtCMCx1fJ4T2541xI4=; b=JHno+Kybi8XaYyqwOdZsYdLcxT5ty4gKhYBhdWk74QdNIC6A8Z5Jmk/CMmkKKGVLrW ifQmLTHjSRV+yHMhDa8EvhjENUuP+QsoiFRN9odPW/oLUoLdwPv9oCMOPj3W18fEVtgA WAzIYUgywVRTr0ILEfbk64liXQIGPTJc6yiQDU2doVg/oofMOm7EfSIpJPcCplZ0gVRg 4OHQ8UWljjrPfdiC7CzmvpHHa+Og9rRQtY5CSq42qPQYeDMTtWRoKaJd2qJr6a8nrqsQ dWFYSg5XqT1TV9IeTPzmpA+VTJeHdJRfe2eYVW5R6lEAx0Tl2EECQnGLUDDeLl0guun3 3+1Q== X-Gm-Message-State: ABy/qLZzEx2MRKoaVwMOXnCBijnyEeU7gFw5nY2irhy/6OkJsjanD3Gw jw4vMclZdAf5FB3T/7njNf8aONdk1gb1+AVefvjMaw== X-Google-Smtp-Source: APBJJlEHWnUxP3CNpH110VR9IOFcKCDj3y0RSICD5X196CVQj2DfSuSMYXTixdZVusBvsAkkuk46WrN4HqVIrU84qoQ= X-Received: by 2002:a25:bc88:0:b0:d14:6e28:69a4 with SMTP id e8-20020a25bc88000000b00d146e2869a4mr584794ybk.29.1690494760452; Thu, 27 Jul 2023 14:52:40 -0700 (PDT) MIME-Version: 1.0 References: <20230726214103.3261108-1-jannh@google.com> <20230726214103.3261108-3-jannh@google.com> In-Reply-To: <20230726214103.3261108-3-jannh@google.com> From: Suren Baghdasaryan Date: Thu, 27 Jul 2023 14:52:26 -0700 Message-ID: Subject: Re: [PATCH 1/2] mm: lock_vma_under_rcu() must check vma->anon_vma under vma lock To: Jann Horn Cc: Andrew Morton , Linus Torvalds , Peter Zijlstra , Matthew Wilcox , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alan Stern , Andrea Parri , Will Deacon , Boqun Feng , Nicholas Piggin , David Howells , Jade Alglave , Luc Maranget , "Paul E. McKenney" , Akira Yokosawa , Daniel Lustig , Joel Fernandes Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 95D6D14000F X-Stat-Signature: 9rib16iuzkzrzbk9m6jar9qp6a7qq94g X-HE-Tag: 1690494761-210319 X-HE-Meta: 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 apqThtwd 6Qqn+cylVn3CuFIvqHUxqOjPyqXeK07Uvy1cSAK5EiU/pfXCxoxob+HwoRkvpdEtGm6k8hTo9tSBQojc7MSAb8I+72tH1k8HUEuBtFHC7DG2dObAxthj0p/lnTW687T9AD5O5NffBF20sfXA58Taf4N8JkALBPmWJ8DRtU/GwMHon+fPU9OSTtIRc8yNvk7Qy1D5biDG0KHvN6C1N2L8rJkZsVG//W5NIvD6cCv1mMe4cZiVIY/RRV1OlK7avH1W+QFpZkjd2+t4mAyVMF1kkeYTrM2jsle7xKCNVaFzZxjaPGfshh1kohujPGbgIft+ABsvq2UTdniQaJbZEYNrui+Oc9EvphycqhPqKg530HHfBz5RaVjdxtfktpi3fQ54UF04vqp5cZJI7H/XHLgYbVwu/MXvuLaqiHAJGSUaX4xQvKlo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jul 26, 2023 at 2:42=E2=80=AFPM Jann Horn wrote: > > lock_vma_under_rcu() tries to guarantee that __anon_vma_prepare() can't > be called in the VMA-locked page fault path by ensuring that > vma->anon_vma is set. > However, this check happens before the VMA is locked, which means a > concurrent move_vma() can concurrently call unlink_anon_vmas(), which > disassociates the VMA's anon_vma. > > This means we can get UAF in the following scenario: > > THREAD 1 THREAD 2 > =3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D > > lock_vma_under_rcu() > rcu_read_lock() > mas_walk() > check vma->anon_vma > > mremap() syscall > move_vma() > vma_start_write() > unlink_anon_vmas() > > > handle_mm_fault() > __handle_mm_fault() > handle_pte_fault() > do_pte_missing() > do_anonymous_page() > anon_vma_prepare() > __anon_vma_prepare() > find_mergeable_anon_vma() > mas_walk() [looks up VMA X] > > munmap() syscall (deletes VMA X) > > reusable_anon_vma() [called on freed VMA X] > > This is a security bug if you can hit it, although an attacker would > have to win two races at once where the first race window is only a > few instructions wide. > > This patch is based on some previous discussion with Linus Torvalds on > the security list. > > Cc: stable@vger.kernel.org > Fixes: 5e31275cc997 ("mm: add per-VMA lock and helper functions to contro= l it") > Signed-off-by: Jann Horn Reviewed-by: Suren Baghdasaryan > --- > mm/memory.c | 28 ++++++++++++++++------------ > 1 file changed, 16 insertions(+), 12 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 01f39e8144ef..603b2f419948 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5393,27 +5393,28 @@ struct vm_area_struct *lock_vma_under_rcu(struct = mm_struct *mm, > if (!vma_is_anonymous(vma) && !vma_is_tcp(vma)) > goto inval; > > - /* find_mergeable_anon_vma uses adjacent vmas which are not locke= d */ > - if (!vma->anon_vma && !vma_is_tcp(vma)) > - goto inval; > - > if (!vma_start_read(vma)) > goto inval; > > + /* > + * find_mergeable_anon_vma uses adjacent vmas which are not locke= d. > + * This check must happen after vma_start_read(); otherwise, a > + * concurrent mremap() with MREMAP_DONTUNMAP could dissociate the= VMA > + * from its anon_vma. > + */ > + if (unlikely(!vma->anon_vma && !vma_is_tcp(vma))) > + goto inval_end_read; > + > /* > * Due to the possibility of userfault handler dropping mmap_lock= , avoid > * it for now and fall back to page fault handling under mmap_loc= k. > */ > - if (userfaultfd_armed(vma)) { > - vma_end_read(vma); > - goto inval; > - } > + if (userfaultfd_armed(vma)) > + goto inval_end_read; > > /* Check since vm_start/vm_end might change before we lock the VM= A */ > - if (unlikely(address < vma->vm_start || address >=3D vma->vm_end)= ) { > - vma_end_read(vma); > - goto inval; > - } > + if (unlikely(address < vma->vm_start || address >=3D vma->vm_end)= ) > + goto inval_end_read; > > /* Check if the VMA got isolated after we found it */ > if (vma->detached) { > @@ -5425,6 +5426,9 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm= _struct *mm, > > rcu_read_unlock(); > return vma; > + > +inval_end_read: > + vma_end_read(vma); > inval: > rcu_read_unlock(); > count_vm_vma_lock_event(VMA_LOCK_ABORT); > -- > 2.41.0.487.g6d72f3e995-goog >