From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id ACFAC2877D9; Tue, 4 Nov 2025 03:36:19 +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=1762227382; cv=none; b=NOgKygHQ2BbBxnWoEUfZL+4rSgoa/Iv1Gt0tPYh8tUYy39ouWHz+MiJLXqQZfGTzPVoJwlfUJbn3ALyOef4r//n8k+pIObLuNHGd29p0q+nCj2iorOKlolNLyBUo0XErsVNJQJmBwkl1tKr/xIjZUjSk32QoCei5wxU3AMhm598= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762227382; c=relaxed/simple; bh=yWT+oaIy6Zb9pUiGpobZ0cTjAIt5SrcuCSvT/kJOCeI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ko3yIHyw9rymvbJgyTaVzWrAlRulhphWfafAkMMepZjgrIq5osA3Hiu9ZO93ID9b99c3dG9cTzThKXg4jHDZ8yqB0bCJXaFnlMlxzk7AC3ZC+Sxp/NcYEq1TGyBfDdPM4neN/34x8iTLOuGsQzfdPLsY+jYKjpE/YEw81LQZPXM= 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 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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 >