From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (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 9BFDE33987E for ; Fri, 9 Oct 2026 15:16:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791558967; cv=none; b=dPIYA0au7BfQupjdEA4NulHSvreIbCmnbJY+pfaukH1/sfxNSin61cEe9DmE+veju1BxS5iNFuCc/3EPieYAGXU/kVIj1rcSjvJKOiYHYAA5SoGBYmup47FYC7vwtCcJtc7RaZknSLDomoxz5+JYyBkkQxyrUe+xWqxEQi1gfQs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791558967; c=relaxed/simple; bh=dQsifwyyig8YpGKxzBzm59+Ftc6+jRRMixF5I9e5kvA=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=ZK+tuuJSzD8FSuaVJaHiP3zKP/IyX/VSfobwuknlYE4ueT/8Lj7E17hPxg5+nXOxo44lZS9pxARWlEiJHLZ3sfQyQZYxQzxTmj06d1cmnIkuTtzotMU+NCXOl4nCfw2gEDxCkIbfor3lu3Nglw9bSsBRtoQI+PHer2WbSHR0iWM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--ardb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=kIRlvsAj; arc=none smtp.client-ip=209.85.208.72 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--ardb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="kIRlvsAj" Received: by mail-ed1-f72.google.com with SMTP id 4fb4d7f45d1cf-6a9caf60126so6766847a12.1 for ; Fri, 09 Oct 2026 08:16:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1791558963; x=1792163763; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=Elt82oVIJIDR2UH2RaIC/yk8bP6X4zNjSmosDoHpGoA=; b=kIRlvsAj8rrGC27TTKFY8+cBhi/MzSA8y2c1WVz0878mj3+faHrTFoo8YmLMar8QFw nXbkzhzqwiOjy8b9pIfXEV8s6JUizXtDv4xC1OLhIH/0SyH9r551FA/XRl/T6gyBvysn qBX2qPkavlNrP7icdegaK1S5ynHM1r6hVF9Hbga3ooo/MHioX7gtJuGuVp/SmbGXx5hY z738YFvR+Oo/J7XLWZZKTdQJm4qdQ+cs4gVJzl/10Yn64fg2AdCPrSBSlwdput63eVP7 7p01liDlw4i2Q1OXxVWlwOZrvLE7hKVlJjXtRNXt/YLkkO/7bDWmRH/CVjIDlcgRRUwI KQtA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791558963; x=1792163763; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=Elt82oVIJIDR2UH2RaIC/yk8bP6X4zNjSmosDoHpGoA=; b=zDxqMHOnLvYlKBSDar8Qp3tIXEJqeA60Tl48MsREG/7NcNiM5dVsPCWgDt7UsSJiZt 5mp/CucXeVqGYlm84+k0QS+wGp54eB/sf7lUq2NXmOcpIhUns9sZ7O9C0DWo+VgwC5/Y fLr8O+J5hlG5USSejSCdzbCJjqL3JIlawCD9JJrkeR2ho6qqkxuCMZNUbYWhA5agq+Zm 8tZ3834YeTWi/MgWJIcuYFJ4AKZt3TpDSj3P4kUQj3WD3amUJDuj3OgV0T7KpBiMqUx8 diNod/rnGDd8omQHpICgpZXUGnwrCu0KRjPWni5NYm5EEXnYTihgRStEJSDsV1z7TGdD TrWQ== X-Gm-Message-State: AFq9FYII3ErhNcYfTT0tVRwlwFK7JkOdfXOrz337XSOEzqXjTgQJwV8c efHpXMDcqRbDEPB0urH2OktPPtDfYZV2s0GlZpX9BaR10wr4J3QnwP+3UXafd5j2W1skEA9oNKD j2PttjThh/jieC9LU/Zt+D/4tTLUCkiMmUwfiPUzHtOZAhhUnZsuFTGM4absxe2NKLiXacuKQCf iQJMkFXXpcN2JhNNsfOJTVK4OXmn1S0w== X-Received: from edxs24.prod.google.com ([2002:a05:6402:1658:b0:6ac:c30e:4ee2]) (user=ardb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6402:4582:b0:6af:dc52:3639 with SMTP id 4fb4d7f45d1cf-6b17c27f1a8mr1833622a12.40.1791558963095; Fri, 09 Oct 2026 08:16:03 -0700 (PDT) Date: Fri, 9 Oct 2026 17:16:01 +0200 Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.56.0.385.gd3acb90ef8-goog Message-ID: <20261009151600.351766-2-ardb+git@google.com> Subject: [PATCH] arm64/efi: Clear PTE_WRITE when applying EFI_MEMORY_RO From: Ard Biesheuvel To: linux-efi@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com, will@kernel.org, catalin.marinas@arm.com, Ard Biesheuvel Content-Type: text/plain; charset="UTF-8" From: Ard Biesheuvel set_permissions() sets PTE_RDONLY for regions that the Memory Attributes Table describes as read-only, but leaves PTE_WRITE set. PTE_WRITE is the DBM bit, so when hardware dirty state management is enabled (TCR_EL1.HD), such a descriptor is writable-clean rather than read-only, and a write by the firmware will be permitted by the hardware (which marks the entry dirty) instead of faulting. Clear PTE_WRITE as well, as pte_wrprotect() does. Cc: Signed-off-by: Ard Biesheuvel --- arch/arm64/kernel/efi.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c index 0ec90fd1754e..6f34aef3d04e 100644 --- a/arch/arm64/kernel/efi.c +++ b/arch/arm64/kernel/efi.c @@ -117,8 +117,14 @@ static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data) const efi_memory_desc_t *md = spd->md; pte_t pte = __ptep_get(ptep); + /* + * Clear PTE_WRITE as well: it doubles as the DBM bit, and leaving it + * set would permit the hardware to make the mapping writable again + * when TCR_EL1.HD is set. + */ if (md->attribute & EFI_MEMORY_RO) - pte = set_pte_bit(pte, __pgprot(PTE_RDONLY)); + pte = set_pte_bit(clear_pte_bit(pte, __pgprot(PTE_WRITE)), + __pgprot(PTE_RDONLY)); if (md->attribute & EFI_MEMORY_XP) pte = set_pte_bit(pte, __pgprot(PTE_PXN)); else if (system_supports_bti_kernel() && spd->has_bti) -- 2.56.0.385.gd3acb90ef8-goog