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 0F58247F77E; Thu, 20 Aug 2026 17:30:21 +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=1787247022; cv=none; b=DadMsR9QrSl4w7eX6CSp1GdbRqubRWzroWJ7+3s4SQlE6zBHXaLK9ppfr1CLZWQPNkZoV14ABa37iZPL5rmBHmffFtxt3zkb0A/kj2u6oGHtKHvZxAbAvvpBSkK7uGKt84qaxkp34Kqbglz7fFHgm0xjIbDYWX4bn2V3KxqzRE4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787247022; c=relaxed/simple; bh=BRzOJUPgATAoMXBe2QLrL6LUdo7g4lMPkslgFA9Ni8k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nusV14LwPXNgLpIktKV4F8QPLonaU0rVRsWp6IgxfeEqVnLAt+SyBUG8I3rh4zn3Q4xTQzWx4Mwz5OxlG7i0TLlurV/L+yquBh3FwtwZmtQqKPFi8vLLoS1cgbbHdC8RLZdU3kPRY+Rs9qArghpNYDMlPCNKlPIAoIGgYtG6r1s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1jHb7zhW; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1jHb7zhW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 635CF1F000E9; Thu, 20 Aug 2026 17:30:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787247021; bh=dFnDXDP0KRJ3vzZQ69jqAo82S4XEp7mUXz91k4u98QY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=1jHb7zhW7SuPz2BjYUPMfmtGm7V+FnsN2FoK2W7ehTabcuukX9614gfvqjkLBOzt9 pHyrwlRh8dCB71mGYDScLqnmcOn0k50cbSCX0wAWqLmskRE9RGUu5PdtyoFfxq2Uxa 4e2mVmOcJMEDDhuoNz81r7xRMKfLFIhpcElRxISc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "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 6.12 121/220] userfaultfd: prevent registration of special VMAs Date: Thu, 20 Aug 2026 16:55:11 +0200 Message-ID: <20260820145227.112276886@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260820145223.480031205@linuxfoundation.org> References: <20260820145223.480031205@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ 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 Signed-off-by: Greg Kroah-Hartman --- include/linux/userfaultfd_k.h | 6 ++++++ 1 file changed, 6 insertions(+) --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -216,6 +216,12 @@ static inline bool vma_can_userfault(str 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)