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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250211_091506_627650_8111CE6E X-CRM114-Status: GOOD ( 15.42 ) 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: , Cc: linux-arm-kernel@lists.infradead.org, Alexandre Belloni , Ryan Roberts , open list , Hugh Dickins , Muchun Song , Ezra Buehler , Matthew Wilcox , Claudiu Beznea , "Vishal Moola \(Oracle\)" , linux-mm@kvack.org, Peter Xu , "Mike Rapoport \(Microsoft\)" , Andrew Morton , Vlastimil Babka Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 11.02.25 04:45, Qi Zheng wrote: > Hi Russell, > > On 2025/2/11 01:03, Russell King (Oracle) wrote: >> On Mon, Feb 10, 2025 at 05:49:38PM +0100, Ezra Buehler wrote: >>> When running vanilla Linux 6.13 or newer (6.14-rc2) on the >>> AT91SAM9G25-based GARDENA smart Gateway, we are seeing a NULL pointer >>> dereference resulting in a kernel panic. The culprit seems to be commit >>> fc9c45b71f43 ("arm: adjust_pte() usepte_offset_map_rw_nolock()"). >>> Reverting the commit apparently fixes the issue. >> >> The blamed commit is buggy: >> >> arch/arm/include/asm/tlbflush.h: >> #define update_mmu_cache(vma, addr, ptep) \ >> update_mmu_cache_range(NULL, vma, addr, ptep, 1) >> >> So vmf can be NULL. This didn't used to matter before this commit, >> because vmf was not used by ARM's update_mmu_cache_range(). However, >> the commit introduced a dereference of it, which now causes a NULL >> point dereference. >> >> Not sure what the correct solution is, but at a guess, both: >> >> if (ptl != vmf->ptl) >> >> need to become: >> >> if (!vmf || ptl != vmf->ptl) > > No, we can't do that, because without using split PTE locks, we would > use shared mm->page_table_lock, which would create a deadlock. Maybe we can simply special-case on CONFIG_SPLIT_PTE_PTLOCKS ? if (IS_ENABLED(CONFIG_SPLIT_PTE_PTLOCKS)) { ... } -- Cheers, David / dhildenb 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E81BFC0219B for ; Tue, 11 Feb 2025 09:15:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5CCBA280003; Tue, 11 Feb 2025 04:15:08 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 57BAB280001; Tue, 11 Feb 2025 04:15:08 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4431B280003; Tue, 11 Feb 2025 04:15:08 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 26803280001 for ; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 2984640011 X-Stat-Signature: umimdth7z1wd597m9skt1qk7ziifnf83 X-Rspamd-Server: rspam03 X-HE-Tag: 1739265304-158718 X-HE-Meta: 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 J41v1Pz3 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11.02.25 04:45, Qi Zheng wrote: > Hi Russell, > > On 2025/2/11 01:03, Russell King (Oracle) wrote: >> On Mon, Feb 10, 2025 at 05:49:38PM +0100, Ezra Buehler wrote: >>> When running vanilla Linux 6.13 or newer (6.14-rc2) on the >>> AT91SAM9G25-based GARDENA smart Gateway, we are seeing a NULL pointer >>> dereference resulting in a kernel panic. The culprit seems to be commit >>> fc9c45b71f43 ("arm: adjust_pte() usepte_offset_map_rw_nolock()"). >>> Reverting the commit apparently fixes the issue. >> >> The blamed commit is buggy: >> >> arch/arm/include/asm/tlbflush.h: >> #define update_mmu_cache(vma, addr, ptep) \ >> update_mmu_cache_range(NULL, vma, addr, ptep, 1) >> >> So vmf can be NULL. This didn't used to matter before this commit, >> because vmf was not used by ARM's update_mmu_cache_range(). However, >> the commit introduced a dereference of it, which now causes a NULL >> point dereference. >> >> Not sure what the correct solution is, but at a guess, both: >> >> if (ptl != vmf->ptl) >> >> need to become: >> >> if (!vmf || ptl != vmf->ptl) > > No, we can't do that, because without using split PTE locks, we would > use shared mm->page_table_lock, which would create a deadlock. Maybe we can simply special-case on CONFIG_SPLIT_PTE_PTLOCKS ? if (IS_ENABLED(CONFIG_SPLIT_PTE_PTLOCKS)) { ... } -- Cheers, David / dhildenb