From patchwork Tue Feb 1 11:44:00 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jianyong Wu X-Patchwork-Id: 12731601 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 EDC0DC433EF for ; Tue, 1 Feb 2022 11:45:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:List-Subscribe:List-Help: List-Post:List-Archive:List-Unsubscribe:List-Id:Message-Id:Date:Subject:Cc:To :From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=3AYA57TekkfLqHsfrcURQqBg4uGD5lsew3kDbuDndqI=; b=vHHsb7z1uigvCE slGx/5KckYpgL9ykUOkpkakEht0OLZJmKvM1gLU7BKKGWbCqHXScxQhlO2sWVnIk3tcRnGCGvdH6E binUcyi+uRp4BDgv9XespK/LxPdyAocoQir2bcyiv+mVEMsrPAXFfoZKog56IGfu1RVmrALMeuCSS bTxFo9oO+AZkrV4j2zk0fxXosdRHIsn7cxVSIuti7PXqcasV5xTuCcgAwMJMs9DLnfZGC1cMzBJNk wSN6rkcArrPzTpioxINBiZ01HghUXmEwfWR3HMvh/p87WlNsS1r2asKzXubhpW5sh0FmpCH0Sm7DB NnMwe9iADWIT//P1UkwA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nEra6-00BsUw-Po; Tue, 01 Feb 2022 11:44:18 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nEra3-00BsTz-7q for linux-arm-kernel@lists.infradead.org; Tue, 01 Feb 2022 11:44:16 +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 8C457113E; Tue, 1 Feb 2022 03:44:11 -0800 (PST) Received: from entos-thunderx2-desktop.shanghai.arm.com (entos-thunderx2-desktop.shanghai.arm.com [10.169.212.232]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id A64993F73B; Tue, 1 Feb 2022 03:44:07 -0800 (PST) From: Jianyong Wu To: catalin.marinas@arm.com, will@kernel.org, anshuman.khandual@arm.com, akpm@linux-foundation.org, david@redhat.com, ardb@kernel.org Cc: quic_qiancai@quicinc.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, gshan@redhat.com, justin.he@arm.com, jianyong.wu@arm.com, nd@arm.com Subject: [PATCH] [PATCH v4] arm64/mm: avoid fixmap race condition when create pud mapping Date: Tue, 1 Feb 2022 19:44:00 +0800 Message-Id: <20220201114400.56885-1-jianyong.wu@arm.com> X-Mailer: git-send-email 2.17.1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220201_034415_368763_51CC2EF9 X-CRM114-Status: UNSURE ( 9.64 ) X-CRM114-Notice: Please train this message. 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: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The 'fixmap' is a global resource and is used recursively by create pud mapping(), leading to a potential race condition in the presence of a concurrent call to alloc_init_pud(): kernel_init thread virtio-mem workqueue thread ================== =========================== alloc_init_pud(...) alloc_init_pud(...) pudp = pud_set_fixmap_offset(...) pudp = pud_set_fixmap_offset(...) READ_ONCE(*pudp) pud_clear_fixmap(...) READ_ONCE(*pudp) // CRASH! As kernel may sleep during creating pud mapping, introduce a mutex lock to serialise use of the fixmap entries by alloc_init_pud(). However, there is no need for locking in early boot stage and it doesn't work well with KASLR enabled when early boot. So, enable lock when system_state doesn't equal to "SYSTEM_BOOTING". Signed-off-by: Jianyong Wu Reviewed-by: Catalin Marinas --- Change log: from v3 to v4: conditionally enable lock as we doesn't need lock when early boot. from v2 to v3: change spin lock to mutex lock as kernel may sleep when create pud map. --- arch/arm64/mm/mmu.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index acfae9b41cc8..1681430ecab7 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -63,6 +63,7 @@ static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused; static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused; static DEFINE_SPINLOCK(swapper_pgdir_lock); +static DEFINE_MUTEX(fixmap_lock); void set_swapper_pgd(pgd_t *pgdp, pgd_t pgd) { @@ -329,6 +330,12 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end, } BUG_ON(p4d_bad(p4d)); + /* + * No need for locking during early boot. And it doesn't work as + * expected with KASLR enabled. + */ + if (system_state != SYSTEM_BOOTING) + mutex_lock(&fixmap_lock); pudp = pud_set_fixmap_offset(p4dp, addr); do { pud_t old_pud = READ_ONCE(*pudp); @@ -359,6 +366,8 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end, } while (pudp++, addr = next, addr != end); pud_clear_fixmap(); + if (system_state != SYSTEM_BOOTING) + mutex_unlock(&fixmap_lock); } static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,