From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 BED18347529 for ; Sat, 8 Aug 2026 02:52:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786157555; cv=none; b=OBK4780810HhGwYLhuNItX3KzI35G5LxjQdmGFKAwfphF7jHDJQpJcMJ4a0c+T31sP8oWAMSqv6aZVvChRQ10kGeShXan1WSMEZsbhZGYspfZonQIEfB5dPbXu7WgUp5nE11x2JLmExGE0C6DEy8tSlKJ2954q4T1APmDXbNPhA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786157555; c=relaxed/simple; bh=iofG20uerzb1i9MRCHhqTyWQ0ETuuhwjR0EMq9C2D+8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sLKppoM2H/tgzHAKGUBBft3g+lwNK1vCHtu/Wyj6TVXvVWFqIng1pTVLlxnthv7xEZo7Te5/7CkcyeNajSVl6SXXZEPHAVc8F7Le1651+tvJ17L16zEcse8kWeCSy391EJMzbmVAQ7n/eUwXt7E6sXA7NI8IrJHi/SYZ53zU3BY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ES+J32oN; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ES+J32oN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 275E81F00A3A; Sat, 8 Aug 2026 02:52:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786157554; bh=lISNuSz9U27P9mwMb7fnjbz85WqTN7mlQXzGYwEnFpQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ES+J32oNDVT9MpaQaFN+TcavA5CUyZSQGeWWUUOjhMLttJPXHIitU/H3UckxQuqA5 p/QrFDP/QT43J1+4qQIeHwxnOag3p/NzRnCe2e6G95hDZqtiwxY2yDS5SfC/wENf+7 rQgnHhZOWdCOmhp7E/2/7yo3TFqkN+ruCrwJqK+AG7GD1zBGqNC0H9tU0gbPAA7+NT pAATz+9ozYw/19nDlExyoOOYkrw8lDxSpMy+r8IsaJInybIAWDp1VpEhchdItgWK55 tCQogdg6kh5I/Dy6Fkb79Bp2r1isGl5h5ac+80Xjb+txNqT4zutUDElOlvl3aQFWtI F6veqhxH8aFVQ== From: Sasha Levin To: stable@vger.kernel.org Cc: "Mike Rapoport (Microsoft)" , vova tokarev , "David Hildenbrand (Arm)" , Lorenzo Stoakes , Al Viro , Christian Brauner , Jan Kara , Linus Torvalds , Oleg Nesterov , Peter Xu , Andrew Morton , Sasha Levin Subject: [PATCH 6.12.y 2/2] userfaultfd: prevent registration of special VMAs Date: Fri, 7 Aug 2026 22:52:30 -0400 Message-ID: <20260808025230.4028587-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260808025230.4028587-1-sashal@kernel.org> References: <2026072906-scheming-vocation-25cd@gregkh> <20260808025230.4028587-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Mike Rapoport (Microsoft)" [ Upstream commit 3c58f641e813c3c71039f8fd4d4e2a3aab713288 ] Vova Tokarev says: userfaultfd allows registration on shadow stack VMAs. With userfaultfd access, you can register on the shadow stack, discard a page ... and inject a page with chosen return addresses via UFFDIO_COPY. Update vma_can_userfault() to reject VM_SHADOW_STACK. While on it, also reject VM_SPECIAL so that if a driver would implement vm_uffd_ops, it wouldn't be possible to register special VMAs with userfaultfd. Since VM_SPECIAL includes VM_DONTEXPAND which is set but hugetlb, exclude hugetlb VMAs from the check for VM_SPECIAL. Link: https://lore.kernel.org/20260618095017.2553004-1-rppt@kernel.org Fixes: 54007f818206 ("mm: Introduce VM_SHADOW_STACK for shadow stack memory") Signed-off-by: Mike Rapoport (Microsoft) Reported-by: vova tokarev Acked-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes Cc: Al Viro Cc: Christian Brauner Cc: Jan Kara Cc: Linus Torvalds Cc: Mike Rapoport Cc: Oleg Nesterov Cc: Peter Xu Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin --- include/linux/userfaultfd_k.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 75342022d1441..8ff68ce1860be 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -216,6 +216,12 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma, unsigned long vm_flags, bool wp_async) { + if (vma->vm_flags & VM_SHADOW_STACK) + return false; + + if (!is_vm_hugetlb_page(vma) && (vma->vm_flags & VM_SPECIAL)) + return false; + vm_flags &= __VM_UFFD_FLAGS; if (vm_flags & VM_DROPPABLE) -- 2.53.0