From nobody Wed Dec 17 08:51:12 2025 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 301D718B464 for ; Thu, 3 Apr 2025 05:29:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743658151; cv=none; b=D2euNz4s3Nf9dIvARyX0ADbmOvJVm3WPD19qayJAaUwOq1W003XyeH4UY6NcYAx/d75ju/HkuO/5RXdXXuLjUTCH5P8fX/vpm6dfUNeB0nb3GKT6e2a+M2wq1Rlin3G7ekS6jLDVYjYrgdhwRx92zPBYXQuqIo9rUIqTMrp6LpU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743658151; c=relaxed/simple; bh=D1TYYNwMGMW3cQvKYmEcax+Gzo3gffvUGzBkP7tjcU8=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=H8Aj7TWiNTBa7FunPaIiVQIh721gv0povW6ghJGHSzdaAO1co0WuPZBsUmC0pkulbwGxZzEGgIIPbHbeQZOKScurc0221mFvZVBKMjLpACc+TzTfkkKP+Yd+viqIrc6H7l5fCgMViaAb331KOecKo6ITH6b7h4BpVSqyLVNGZ+g= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A11FF106F; Wed, 2 Apr 2025 22:29:10 -0700 (PDT) Received: from K4MQJ0H1H2.arm.com (unknown [10.163.46.203]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id AF28C3F694; Wed, 2 Apr 2025 22:29:02 -0700 (PDT) From: Dev Jain To: catalin.marinas@arm.com, will@kernel.org Cc: gshan@redhat.com, rppt@kernel.org, steven.price@arm.com, suzuki.poulose@arm.com, tianyaxiong@kylinos.cn, ardb@kernel.org, david@redhat.com, ryan.roberts@arm.com, urezki@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dev Jain Subject: [PATCH v2] arm64: pageattr: Explicitly bail out when changing permissions for vmalloc_huge mappings Date: Thu, 3 Apr 2025 10:58:44 +0530 Message-Id: <20250403052844.61818-1-dev.jain@arm.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" arm64 uses apply_to_page_range to change permissions for kernel vmalloc map= pings, which does not support changing permissions for block mappings. This functi= on will change permissions until it encounters a block mapping, and will bail out with a warning. Since there are no reports of this triggering, it implies that there are currently no cases of code doing a vmalloc_huge() followed by partial permission change. But this is a footgun waiting to go off, so let's detect it early and avoid the possibility of permissions in an intermediate state. So, explicitly disallow changing permissions for VM_ALLOW_HUGE_VMAP mappings. Reviewed-by: Ryan Roberts Reviewed-by: Mike Rapoport (Microsoft) Signed-off-by: Dev Jain Acked-by: David Hildenbrand Reviewed-by: Anshuman Khandual Reviewed-by: Gavin Shan --- v1->v2: - Improve changelog, keep mention of page mappings in comment arch/arm64/mm/pageattr.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c index 39fd1f7ff02a..04d4a8f676db 100644 --- a/arch/arm64/mm/pageattr.c +++ b/arch/arm64/mm/pageattr.c @@ -96,8 +96,8 @@ static int change_memory_common(unsigned long addr, int n= umpages, * we are operating on does not result in such splitting. * * Let's restrict ourselves to mappings created by vmalloc (or vmap). - * Those are guaranteed to consist entirely of page mappings, and - * splitting is never needed. + * Disallow VM_ALLOW_HUGE_VMAP mappings to guarantee that only page + * mappings are updated and splitting is never needed. * * So check whether the [addr, addr + size) interval is entirely * covered by precisely one VM area that has the VM_ALLOC flag set. @@ -105,7 +105,7 @@ static int change_memory_common(unsigned long addr, int= numpages, area =3D find_vm_area((void *)addr); if (!area || end > (unsigned long)kasan_reset_tag(area->addr) + area->size || - !(area->flags & VM_ALLOC)) + ((area->flags & (VM_ALLOC | VM_ALLOW_HUGE_VMAP)) !=3D VM_ALLOC)) return -EINVAL; =20 if (!numpages) --=20 2.30.2