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[222.155.4.20]) by smtp.gmail.com with ESMTPSA id b29sm7135048pgn.53.2021.09.13.00.21.58 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 13 Sep 2021 00:22:00 -0700 (PDT) Subject: Re: Mainline kernel crashes, was Re: RFC: remove set_fs for m68k To: Finn Thain References: <20210721170529.GA14550@lst.de> <755e55ba-4ce2-b4e4-a628-5abc183a557a@linux-m68k.org> <31f27da7-be60-8eb-9834-748b653c2246@linux-m68k.org> <977bb34f-6de9-3a9e-818f-b1aa0758f78f@gmail.com> <42b30d4f-b871-51ea-1b0e-479f4fe096eb@gmail.com> <7ac7a41a-53f9-b13c-83fa-2c6b8ef2b90@linux-m68k.org> <0477f373-86c9-dacb-a7b1-25fe4b3befd3@gmail.com> <2c624213-6a4-799c-45e-a1be578dd5f@linux-m68k.org> <82f6f161-b9e0-bf9b-3c20-aa2ce810d99a@gmail.com> <4564a46-2115-9058-2a9-2d77736291c@linux-m68k.org> Cc: linux-m68k@vger.kernel.org From: Michael Schmitz Message-ID: Date: Mon, 13 Sep 2021 19:20:25 +1200 User-Agent: Mozilla/5.0 (X11; Linux ppc64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <4564a46-2115-9058-2a9-2d77736291c@linux-m68k.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org Hi Finn, On 13/09/21 17:22, Finn Thain wrote: > On Mon, 13 Sep 2021, Michael Schmitz wrote: > >>> >>> [23982.680000] list_add corruption. next->prev should be prev >>> (00b51e98), but was 00bb22d8. (next=00b75cd0). >> >> I chased a similar list corruption bug (shadow LRU list corrupt in >> mm/workingset.c:shadow_lru_isolate()) in 4.10. I believe that was >> related to an out of bounds memory access - maybe get_reg() from >> drivers/char/random.c but it might have been something else. >> >> That bug had disappeared in 4.12, haven't seen it ever since. >> > > Do all of your builds have BUG_ON_DATA_CORRUPTION and DEBUG_LIST enabled? None had, but that particular list corruption had generated warnings, and null pointer accesses. __list_del() uses WRITE_ONCE() now, can't remember that from 4.10 (but the log for linux/list.h doesn't mention adding WRITE_ONCE so I suppose it must have been there). > >> >> Incidentally - have you ever checked whether Al Viro's signal handling >> fixes have an impact on these bugs? >> > > I will try that patch series if you think it is related. Initial tests look promising (but I've said that before). > So far the problem seems to be confined to one machine. Stress tests on > other mac models did not yet reproduce the problem. Yes, that's suspicious. I'll keep you posted. Cheers, Michael