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 AB85C2F659C for ; Tue, 4 Nov 2025 13:14:18 +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=1762262060; cv=none; b=joV+GKYvrHBgy+IfRyE4KWHvCEKA4tHnn7cb8p8Pr2o8x9scqYXVkq3F0UcW8LtbrXfftfLBP+KpGb6bKSe3/JDBDMFF9ORbjU/HtNqiLLjU3aB74D4LbrTwazrf3elaC13m/3poK+utWyYHyk17bT4WxgjvszdvBluiLmN4Amg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762262060; c=relaxed/simple; bh=ntRz6jITIbBBBGOIaf9xFjE4nod5orCM61laMH9WhBs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=a6v/LMvW7AThTvVsVPJDGdwSPrWNlmymmoAIZj+W2KQpHrPkb7EKEazsRgRc2Ob3wHOiEp4G+nnM4xPClDAztkKToV1VIbxp9ot4hmyPTV8QlFOQv+BfE+Xl4jHCmbSiawKGOMrU+AVActiS3MBCOUyRQYNGguaMO134Ji96mxQ= 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 11CDA1CE0; Tue, 4 Nov 2025 05:14:10 -0800 (PST) Received: from [10.1.31.224] (XHFQ2J9959.cambridge.arm.com [10.1.31.224]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EC0DE3F66E; Tue, 4 Nov 2025 05:14:16 -0800 (PST) Message-ID: Date: Tue, 4 Nov 2025 13:14:15 +0000 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: kprobes: check the return value of set_memory_rox() Content-Language: en-GB To: Yang Shi , catalin.marinas@arm.com, will@kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20251103194505.4077265-1-yang@os.amperecomputing.com> From: Ryan Roberts In-Reply-To: <20251103194505.4077265-1-yang@os.amperecomputing.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 03/11/2025 19:45, Yang Shi wrote: > Since commit a166563e7ec3 ("arm64: mm: support large block mapping when > rodata=full"), __change_memory_common has more chance to fail due to > memory allocation fialure when splitting page table. So check the return > value of set_memory_rox(), then bail out if it fails otherwise we may have > RW memory mapping for kprobes insn page. > > Fixes: 195a1b7d8388 ("arm64: kprobes: call set_memory_rox() for kprobe page") > Signed-off-by: Yang Shi This patch looks correct so: Reviewed-by: Ryan Roberts but, I think I see an separate issue below... > --- > I actually epxected 195a1b7d8388 ("arm64: kprobes: call set_memory_rox() > for kprobe page") can be merged in 6.17-rcX, so I just restored it to > before commit 10d5e97c1bf8 ("arm64: use PAGE_KERNEL_ROX directly in > alloc_insn_page"), however it turned out to be merged in 6.18-rc1 and it > is after commit a166563e7ec3 ("arm64: mm: support large block mapping when > rodata=full"). So I made the fix tag point to it. > And I don't think we need to backport this patch to pre-6.18. > > arch/arm64/kernel/probes/kprobes.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c > index 8ab6104a4883..43a0361a8bf0 100644 > --- a/arch/arm64/kernel/probes/kprobes.c > +++ b/arch/arm64/kernel/probes/kprobes.c > @@ -49,7 +49,10 @@ void *alloc_insn_page(void) > addr = execmem_alloc(EXECMEM_KPROBES, PAGE_SIZE); > if (!addr) > return NULL; > - set_memory_rox((unsigned long)addr, 1); > + if (set_memory_rox((unsigned long)addr, 1)) { How does x get cleared when freeing this memory? arm64's set_memory_x() sets PTE_MAYBE_GP and clears PTE_PXN. The only function that will revert that is set_memory_nx(). But that only gets called from module_enable_data_nx() (which I don't think is applicable here) and execmem_force_rw() - but only if CONFIG_ARCH_HAS_EXECMEM_ROX is enabled, which I don't think it is for arm64? So I think once we flip a page executable, it will be executable forever? Do we need to modify set_direct_map_default_noflush() to make the memory nx? Then vm_reset_perms() will fix it up at vfree time? Thanks, Ryan > + execmem_free(addr); > + return NULL; > + } > return addr; > } >