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From: Roman Gushchin To: Erhard Furtner Cc: linux-mm@kvack.org Subject: Re: [bisected] clang 16 built kernel crashes w. "BUG: kernel NULL pointer dereference, address: 00000007", gcc 13 built kernel with same config boots fine (6.7-rc1, x86_32) Message-ID: References: <20231115011506.0edd8870@yea> <20231115234648.4eb10131@yea> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231115234648.4eb10131@yea> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 7AED740005 X-Stat-Signature: fu4xtyi9u1z6psz1qizhao9pzzea7yr3 X-Rspam-User: X-HE-Tag: 1700103612-342345 X-HE-Meta: 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 sH/TN/us QxLqySxruMZZGwH8Ge7QL6alqhSJjYIEXZB0P64LoM51Olv3+bzxXoffZ4qZta84CxyWT+Ge6ptLq9L033Bjz+BExB9d/WrbaKSRpf9V1DhHvqGLJasroCQwt6KSLOZE4fkLzRlz0X81UY0A8WCQzK7A5NOEl9ynMC3HsJ2GGu3Iiay3WaVPTr2NRiWfhusz4ghNs69sAKhjWdAw= 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 Wed, Nov 15, 2023 at 11:46:48PM +0100, Erhard Furtner wrote: > On Wed, 15 Nov 2023 09:33:17 -0800 > Roman Gushchin wrote: > > > Hm, interesting, so the issue is happening only with a kernel built with clang-16 > > but not gcc? And you use 32-bit kernel? Do you know if it's reproducible on a > > 64-bit machine? > > Correct. This only happens when I build the kernel with clang-16. A gcc-13 kernel build using the same .config is fine. That's why I reported it first on https://github.com/ClangBuiltLinux/linux/issues/1959 > > Surprisingly I was indeed able to reproduce the issue on my amd64 box! Ok, I reproduced it too, mastered a fix and sent upstream (you're cc'ed and also mentioned in the commit message). Luckily the problem is trivial, as is the fix. I expect Andrew to pick it up soon, but don't be surprised with some delay - it's a Linux Plumbers week. Thank you for the detailed report and your help with the reproduction of the problem!