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 D4D9AC5DF81 for ; Mon, 24 Aug 2026 16:06:14 +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: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=2HODHgPFWcmpM4OrWXnRIwysDZ/R1pibvtBSqDnsLNw=; b=3V3cc+lHMip3fdPERN/X4Bfrdv Uh8hjJAh3xr7iuzOKlqQtCKQKFrz2LHvPlFW1sTb1CVbxKSBi75CHwCefKFcjQa3XWSzy3sHAHHez eOsxw+uWXu5j+cI9SqdMnXjG7ctPtmYTBr+MlvOEL6kFFvanikVewjXf9cuqNwf7SfXfPHXSW0z1C t/460udIZkab7ov565Z/pqNnwwZLJv/OzdTxJZJCpo0UipOS5c1YrjXV5k0ju0YaYxudlNcKpbOej gfHDvTGWGnUHJNCZ2ShRw8EkJpPc+2IEpxZ41iX7yXHZgys5P6Ae1uOrBb89YEQSCXXS3J1k9DO0D sxJ7tYgw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wyXBY-0000000H0I8-1Lly; Mon, 24 Aug 2026 16:06:08 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wyXBR-0000000H0EY-2z4T for linux-arm-kernel@lists.infradead.org; Mon, 24 Aug 2026 16:06:03 +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 66CAC1BA8; Mon, 24 Aug 2026 09:05:57 -0700 (PDT) Received: from e142334-100.cambridge.arm.com (e142334-100.cambridge.arm.com [10.2.198.93]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 0779D3F85F; Mon, 24 Aug 2026 09:05:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1787587561; bh=nodn3/K9trBK+2wWrkLJGeFqd0INql6u2EHBqnLbWuc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mNGt+rmw+m3ruCwnhja8afWvDAIEG0qPzwe79zxnTqszfW0fgkmn7kM6QqJS5/+ej jNIvAv0fF2vEvSYW8xIbW03slFbzO7/T4PlF0kwnb3MRc3Itdj++wKmSqG7vbSAzpV QanHuh35qBM3KtYjRoJ5HgcXGbly8RHUXJTfOLGQ= From: Muhammad Usama Anjum To: Catalin Marinas , Will Deacon , Mark Rutland , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-arm-kernel@lists.infradead.org (moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)), linux-kernel@vger.kernel.org (open list), bpf@vger.kernel.org (open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)), linux-mm@kvack.org (open list:MEMORY MANAGEMENT - CORE) Cc: Muhammad Usama Anjum Subject: [PATCH 4/7] maccess: Use a scoped guard for page faults Date: Mon, 24 Aug 2026 17:04:49 +0100 Message-ID: <20260824160523.3907021-5-usama.anjum@arm.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260824160523.3907021-1-usama.anjum@arm.com> References: <20260824160523.3907021-1-usama.anjum@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260824_090601_846525_7932D017 X-CRM114-Status: GOOD ( 10.65 ) 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 Kernel nofault copy and string paths open-code page-fault disable and enable around label-based loops, duplicating cleanup on success and failure. Use a page-fault scope guard instead. Leaving the scope now re-enables page faults on both paths without separate cleanup at the fault label. No functional change. Signed-off-by: Muhammad Usama Anjum --- mm/maccess.c | 53 +++++++++++++++++++++++++--------------------------- 1 file changed, 25 insertions(+), 28 deletions(-) diff --git a/mm/maccess.c b/mm/maccess.c index c59a0e092d24a..f695ceefe6fcc 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -38,18 +38,17 @@ long copy_from_kernel_nofault(void *dst, const void *src, size_t size) if (!size) return 0; - pagefault_disable(); - if (!(align & 7)) - copy_from_kernel_nofault_loop(dst, src, size, u64, Efault); - if (!(align & 3)) - copy_from_kernel_nofault_loop(dst, src, size, u32, Efault); - if (!(align & 1)) - copy_from_kernel_nofault_loop(dst, src, size, u16, Efault); - copy_from_kernel_nofault_loop(dst, src, size, u8, Efault); - pagefault_enable(); + scoped_guard(pagefault) { + if (!(align & 7)) + copy_from_kernel_nofault_loop(dst, src, size, u64, Efault); + if (!(align & 3)) + copy_from_kernel_nofault_loop(dst, src, size, u32, Efault); + if (!(align & 1)) + copy_from_kernel_nofault_loop(dst, src, size, u16, Efault); + copy_from_kernel_nofault_loop(dst, src, size, u8, Efault); + } return 0; Efault: - pagefault_enable(); return -EFAULT; } EXPORT_SYMBOL_GPL(copy_from_kernel_nofault); @@ -73,18 +72,17 @@ long copy_to_kernel_nofault(void *dst, const void *src, size_t size) if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) align = (unsigned long)dst | (unsigned long)src; - pagefault_disable(); - if (!(align & 7)) - copy_to_kernel_nofault_loop(dst, src, size, u64, Efault); - if (!(align & 3)) - copy_to_kernel_nofault_loop(dst, src, size, u32, Efault); - if (!(align & 1)) - copy_to_kernel_nofault_loop(dst, src, size, u16, Efault); - copy_to_kernel_nofault_loop(dst, src, size, u8, Efault); - pagefault_enable(); + scoped_guard(pagefault) { + if (!(align & 7)) + copy_to_kernel_nofault_loop(dst, src, size, u64, Efault); + if (!(align & 3)) + copy_to_kernel_nofault_loop(dst, src, size, u32, Efault); + if (!(align & 1)) + copy_to_kernel_nofault_loop(dst, src, size, u16, Efault); + copy_to_kernel_nofault_loop(dst, src, size, u8, Efault); + } return 0; Efault: - pagefault_enable(); return -EFAULT; } @@ -97,18 +95,17 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count) if (!copy_from_kernel_nofault_allowed(unsafe_addr, count)) return -ERANGE; - pagefault_disable(); - do { - __get_kernel_nofault(dst, src, u8, Efault); - dst++; - src++; - } while (dst[-1] && src - unsafe_addr < count); - pagefault_enable(); + scoped_guard(pagefault) { + do { + __get_kernel_nofault(dst, src, u8, Efault); + dst++; + src++; + } while (dst[-1] && src - unsafe_addr < count); + } dst[-1] = '\0'; return src - unsafe_addr; Efault: - pagefault_enable(); dst[0] = '\0'; return -EFAULT; } -- 2.47.3