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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5A42C47082 for ; Tue, 12 Apr 2022 08:40:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383661AbiDLIhs (ORCPT ); Tue, 12 Apr 2022 04:37:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46348 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356941AbiDLHjf (ORCPT ); Tue, 12 Apr 2022 03:39:35 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8E1B82716D; Tue, 12 Apr 2022 00:10:33 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 06EA361531; Tue, 12 Apr 2022 07:10:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0FCAEC385A5; Tue, 12 Apr 2022 07:10:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649747432; bh=F6q0NgFn3EUSCj5ij3cTfIIF72wNVw0Hn/8yaYM1iPs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TVU1Q0rJpDTgv5xkAP9Ujx75k3Hec0+qb6cw4mogXpIH3ulZwTxftaQtP+/R/cIc4 N1NTyJd20h/GCqyYOMjnyUAgymTTw6WPlySoMMnEKHgICPs4lzr0UbhNJW5dc1uXno TvPwM1ZylwwC/vzG6waS/T/xTxX3PBRonRqt2Vz0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Maxime Bizon , Christophe Leroy , Michael Ellerman , Sasha Levin Subject: [PATCH 5.17 078/343] powerpc/set_memory: Avoid spinlock recursion in change_page_attr() Date: Tue, 12 Apr 2022 08:28:16 +0200 Message-Id: <20220412062953.351886212@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220412062951.095765152@linuxfoundation.org> References: <20220412062951.095765152@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Christophe Leroy [ Upstream commit a4c182ecf33584b9b2d1aa9dad073014a504c01f ] Commit 1f9ad21c3b38 ("powerpc/mm: Implement set_memory() routines") included a spin_lock() to change_page_attr() in order to safely perform the three step operations. But then commit 9f7853d7609d ("powerpc/mm: Fix set_memory_*() against concurrent accesses") modify it to use pte_update() and do the operation safely against concurrent access. In the meantime, Maxime reported some spinlock recursion. [ 15.351649] BUG: spinlock recursion on CPU#0, kworker/0:2/217 [ 15.357540] lock: init_mm+0x3c/0x420, .magic: dead4ead, .owner: kworker/0:2/217, .owner_cpu: 0 [ 15.366563] CPU: 0 PID: 217 Comm: kworker/0:2 Not tainted 5.15.0+ #523 [ 15.373350] Workqueue: events do_free_init [ 15.377615] Call Trace: [ 15.380232] [e4105ac0] [800946a4] do_raw_spin_lock+0xf8/0x120 (unreliable) [ 15.387340] [e4105ae0] [8001f4ec] change_page_attr+0x40/0x1d4 [ 15.393413] [e4105b10] [801424e0] __apply_to_page_range+0x164/0x310 [ 15.400009] [e4105b60] [80169620] free_pcp_prepare+0x1e4/0x4a0 [ 15.406045] [e4105ba0] [8016c5a0] free_unref_page+0x40/0x2b8 [ 15.411979] [e4105be0] [8018724c] kasan_depopulate_vmalloc_pte+0x6c/0x94 [ 15.418989] [e4105c00] [801424e0] __apply_to_page_range+0x164/0x310 [ 15.425451] [e4105c50] [80187834] kasan_release_vmalloc+0xbc/0x134 [ 15.431898] [e4105c70] [8015f7a8] __purge_vmap_area_lazy+0x4e4/0xdd8 [ 15.438560] [e4105d30] [80160d10] _vm_unmap_aliases.part.0+0x17c/0x24c [ 15.445283] [e4105d60] [801642d0] __vunmap+0x2f0/0x5c8 [ 15.450684] [e4105db0] [800e32d0] do_free_init+0x68/0x94 [ 15.456181] [e4105dd0] [8005d094] process_one_work+0x4bc/0x7b8 [ 15.462283] [e4105e90] [8005d614] worker_thread+0x284/0x6e8 [ 15.468227] [e4105f00] [8006aaec] kthread+0x1f0/0x210 [ 15.473489] [e4105f40] [80017148] ret_from_kernel_thread+0x14/0x1c Remove the read / modify / write sequence to make the operation atomic and remove the spin_lock() in change_page_attr(). To do the operation atomically, we can't use pte modification helpers anymore. Because all platforms have different combination of bits, it is not easy to use those bits directly. But all have the _PAGE_KERNEL_{RO/ROX/RW/RWX} set of flags. All we need it to compare two sets to know which bits are set or cleared. For instance, by comparing _PAGE_KERNEL_ROX and _PAGE_KERNEL_RO you know which bit gets cleared and which bit get set when changing exec permission. Reported-by: Maxime Bizon Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/all/20211212112152.GA27070@sakura/ Link: https://lore.kernel.org/r/43c3c76a1175ae6dc1a3d3b5c3f7ecb48f683eea.1640344012.git.christophe.leroy@csgroup.eu Signed-off-by: Sasha Levin --- arch/powerpc/mm/pageattr.c | 32 +++++++++++++------------------- 1 file changed, 13 insertions(+), 19 deletions(-) diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c index 3bb9d168e3b3..85753e32a4de 100644 --- a/arch/powerpc/mm/pageattr.c +++ b/arch/powerpc/mm/pageattr.c @@ -15,12 +15,14 @@ #include +static pte_basic_t pte_update_delta(pte_t *ptep, unsigned long addr, + unsigned long old, unsigned long new) +{ + return pte_update(&init_mm, addr, ptep, old & ~new, new & ~old, 0); +} + /* - * Updates the attributes of a page in three steps: - * - * 1. take the page_table_lock - * 2. install the new entry with the updated attributes - * 3. flush the TLB + * Updates the attributes of a page atomically. * * This sequence is safe against concurrent updates, and also allows updating the * attributes of a page currently being executed or accessed. @@ -28,25 +30,21 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data) { long action = (long)data; - pte_t pte; - spin_lock(&init_mm.page_table_lock); - - pte = ptep_get(ptep); - - /* modify the PTE bits as desired, then apply */ + /* modify the PTE bits as desired */ switch (action) { case SET_MEMORY_RO: - pte = pte_wrprotect(pte); + /* Don't clear DIRTY bit */ + pte_update_delta(ptep, addr, _PAGE_KERNEL_RW & ~_PAGE_DIRTY, _PAGE_KERNEL_RO); break; case SET_MEMORY_RW: - pte = pte_mkwrite(pte_mkdirty(pte)); + pte_update_delta(ptep, addr, _PAGE_KERNEL_RO, _PAGE_KERNEL_RW); break; case SET_MEMORY_NX: - pte = pte_exprotect(pte); + pte_update_delta(ptep, addr, _PAGE_KERNEL_ROX, _PAGE_KERNEL_RO); break; case SET_MEMORY_X: - pte = pte_mkexec(pte); + pte_update_delta(ptep, addr, _PAGE_KERNEL_RO, _PAGE_KERNEL_ROX); break; case SET_MEMORY_NP: pte_update(&init_mm, addr, ptep, _PAGE_PRESENT, 0, 0); @@ -59,16 +57,12 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data) break; } - pte_update(&init_mm, addr, ptep, ~0UL, pte_val(pte), 0); - /* See ptesync comment in radix__set_pte_at() */ if (radix_enabled()) asm volatile("ptesync": : :"memory"); flush_tlb_kernel_range(addr, addr + PAGE_SIZE); - spin_unlock(&init_mm.page_table_lock); - return 0; } -- 2.35.1