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 ACF17263F44 for ; Fri, 7 Aug 2026 03:35:03 +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=1786073706; cv=none; b=tFnXiQBQl8l7eXtcCYhL0vldiZ5S2fYUJIP6gua6ZKNilmmI4T7i8wYyFu17kZu2YAFm4thWvL2/YLgpNKxDfuDI0eBK3wvSN+upkPEmoQr6ZXMhLprfl3jhZt8tZMiyw4F5nojlmVOBRnqWjdEFsGVv8JzMLbFCUF9bwHv6GM4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786073706; c=relaxed/simple; bh=IPcNEwmdmIL6shZkb6brbIxhS8abR99WN46J58FMS7k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iLKksjy9qzHV8v09Pr9kvJN5kfchS5+vHOkCvt1zdqTIdFHPo/aomAc4BaJrBuq5Eir5+ZCnnFbRGi1GdYcz0zj8GVJYND/tuzSnFPGUaLIKAppzAnTwlJulGPqpIP/tlzYu0Vap6BcGDjgv5rk8IsqZiCqUNmGGCgaLI5H4p8I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FRVz93U6; 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="FRVz93U6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 771E01F000E9; Fri, 7 Aug 2026 03:35:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786073702; bh=OVfBD+11YJq18BTWABGGlwvlZc0kzsonAmLIpfHCnTE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FRVz93U6pzZUlKlV0XaGkifjs0J9by02mejeJ3rcWkr1+3U1ml/xTYE6PT7z8b3/b Bw41n/lMVU527PQiyoYl96OrNM9dOLIRvHyDdiExUo43k4V8jBeJdT+j1f07dq9X98 pUzCJudYqx2cl/YRRXFNp7hRI629ebHnHNai2v959ExfNux/8Z/PkXf1I+goXi7GCD SYxt/olPyGcde5SXsMIl6QaWW2XP6Vs41QQKw66FDtN33I4scRDs1yPxYOJSlukCwH CDFAcIgv/AtkYQOWJa1MWSBgzGtiAY0xDdGyyxUrTvgr1bspmYC/b9TYZaENtfU83j 9ZpKNU7TjbgEA== 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 6.18.y] userfaultfd: prevent registration of special VMAs Date: Thu, 6 Aug 2026 23:34:59 -0400 Message-ID: <20260807033459.1725973-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026072906-estranged-sinless-b8ff@gregkh> References: <2026072906-estranged-sinless-b8ff@gregkh> 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 | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index c0e716aec26aa..796a380664bd8 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -214,7 +214,10 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma, { vm_flags &= __VM_UFFD_FLAGS; - if (vma->vm_flags & VM_DROPPABLE) + if (vma->vm_flags & (VM_DROPPABLE | VM_SHADOW_STACK)) + return false; + + if (!is_vm_hugetlb_page(vma) && (vma->vm_flags & VM_SPECIAL)) return false; if ((vm_flags & VM_UFFD_MINOR) && -- 2.53.0