From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 71966CCF9F8 for ; Tue, 4 Nov 2025 03:36:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=d1M5F57ZHwlsPFsFAUa6X/hotEJH+J5eJQO7NQkU2o4=; b=XREUya8AYjuvfe6u9DHs2rvlUt qMu1yFmCIb1y5lOf5NHYJwZvML/iXsb+tIXJht8nV6JjlaPYopJ9OHNtHqTJY20BZLO50qkzFHy9R 5eYaGOuCKxK5Qtq55urGDTv7WbP0+Mh+YH8a6Dku9dpv1NUp8mO9GrlfL2SVIpDACU8gcwXTwzwJ9 9if+owxN/IP5cFRCTjJnylhunMpLmUKLF4qw+KQMg7GfbdUftKYO5WC+CvBPvF+0VIEZhvWkf//5C oKFcQhjvJX1eSHcdwuF5C2BYnc0lOjEFqHuqE0yVYVmJ4ebQm8x0prvkKbQFM1TrYPIdtt+vVQ+LG 7jcOP/Xw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vG7qK-0000000B4K6-16EC; Tue, 04 Nov 2025 03:36:24 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vG7qG-0000000B4Jd-3zum for linux-arm-kernel@lists.infradead.org; Tue, 04 Nov 2025 03:36:22 +0000 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 3549F1C2B; Mon, 3 Nov 2025 19:36:11 -0800 (PST) Received: from [10.164.136.37] (unknown [10.164.136.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 02B543F63F; Mon, 3 Nov 2025 19:36:15 -0800 (PST) Message-ID: Date: Tue, 4 Nov 2025 09:06:12 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64/pageattr: Propagate return value from __change_memory_common To: Yang Shi , Will Deacon Cc: catalin.marinas@arm.com, ryan.roberts@arm.com, rppt@kernel.org, shijie@os.amperecomputing.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20251103061306.82034-1-dev.jain@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251103_193621_038629_CAE9473F X-CRM114-Status: GOOD ( 18.65 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 04/11/25 12:15 am, Yang Shi wrote: > > > On 11/3/25 7:16 AM, Will Deacon wrote: >> On Mon, Nov 03, 2025 at 11:43:06AM +0530, Dev Jain wrote: >>> Post a166563e7ec3 ("arm64: mm: support large block mapping when >>> rodata=full"), >>> __change_memory_common has a real chance of failing due to split >>> failure. >>> Before that commit, this line was introduced in c55191e96caa, still >>> having >>> a chance of failing if it needs to allocate pagetable memory in >>> apply_to_page_range, although that has never been observed to be true. >>> In general, we should always propagate the return value to the caller. >>> >>> Cc: stable@vger.kernel.org >>> Fixes: c55191e96caa ("arm64: mm: apply r/o permissions of VM areas >>> to its linear alias as well") >>> Signed-off-by: Dev Jain >>> --- >>> Based on Linux 6.18-rc4. >>> >>>   arch/arm64/mm/pageattr.c | 5 ++++- >>>   1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c >>> index 5135f2d66958..b4ea86cd3a71 100644 >>> --- a/arch/arm64/mm/pageattr.c >>> +++ b/arch/arm64/mm/pageattr.c >>> @@ -148,6 +148,7 @@ static int change_memory_common(unsigned long >>> addr, int numpages, >>>       unsigned long size = PAGE_SIZE * numpages; >>>       unsigned long end = start + size; >>>       struct vm_struct *area; >>> +    int ret; >>>       int i; >>>         if (!PAGE_ALIGNED(addr)) { >>> @@ -185,8 +186,10 @@ static int change_memory_common(unsigned long >>> addr, int numpages, >>>       if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY || >>>                   pgprot_val(clear_mask) == PTE_RDONLY)) { >>>           for (i = 0; i < area->nr_pages; i++) { >>> - __change_memory_common((u64)page_address(area->pages[i]), >>> +            ret = >>> __change_memory_common((u64)page_address(area->pages[i]), >>>                              PAGE_SIZE, set_mask, clear_mask); >>> +            if (ret) >>> +                return ret; >> Hmm, this means we can return failure half-way through the operation. Is >> that something callers are expecting to handle? If so, how can they tell >> how far we got? > > IIUC the callers don't have to know whether it is half-way or not > because the callers will change the permission back (e.g. to RW) for > the whole range when freeing memory. Yes, it is the caller's responsibility to set VM_FLUSH_RESET_PERMS flag. Upon vfree(), it will change the direct map permissions back to RW. > > Thanks, > Yang > >> >> Will >