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Sun, 16 Apr 2023 16:05:01 -0700 (PDT) Received: from [192.168.10.10] ([37.252.92.4]) by smtp.gmail.com with ESMTPSA id eq17-20020a170907291100b0094efe88a037sm3503048ejc.9.2023.04.16.16.05.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 16 Apr 2023 16:05:01 -0700 (PDT) Message-ID: Date: Mon, 17 Apr 2023 03:04:59 +0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v2] mm: khugepaged: Fix kernel BUG in hpage_collapse_scan_file Content-Language: en-US To: Andrew Morton , Zach O'Keefe Cc: Yang Shi , himadrispandya@gmail.com, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, linux-mm@kvack.org, skhan@linuxfoundation.org, syzbot+9578faa5475acb35fa50@syzkaller.appspotmail.com, Mike Kravetz , "Kirill A. Shutemov" , Matthew Wilcox References: <20230330155305.423051-1-ivan.orlov0322@gmail.com> <20230331013301.ecgkjymaf3ws6rfb@google.com> <20230416113335.caeafda1328fdd4bfe2406e8@linux-foundation.org> From: Ivan Orlov In-Reply-To: <20230416113335.caeafda1328fdd4bfe2406e8@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A20A220007 X-Stat-Signature: fbjfb8b975r3i7xwjicfxwd89zdjzn7w X-HE-Tag: 1681686303-502553 X-HE-Meta: U2FsdGVkX19FK/8bzE1ArUb1zVrQZx/6G8ShcBcGIZ5z6+5Be4rin2SMlaKmSve9zLapkSpXDyZ6MzgUbw1ERn1vKhY1abieFs66EfAN/nm8zTN+gg+/KYLml2K/3iMH5WhiNhlkzBHqdKDBYADzt8ekivbUZEBpxd5l2+byrfktpXHsDROU8yKC6XaNB8GCdl6grxKvmo0hVEgfIBY+Vlv+bftMwWTUieX4Nk5TPwFVxTkHAH3getyrlq3GIuh96TuhIq0XRE5IPfzgPTtCyyOwnNpE4hw3HH7w9TKauYmEEAUj3qRa3Bj3cQnKm4N+zI1UwJMed/5HVFoHjglDwp4R6elmS++82jC2UZk1TOAsUb5qxrdbDWETqafL0C4s9YNlkKxsQoFVQlFoBNB9nO13vYHXlpQW65lEaacQ7F7eGU+52PFDfBFxKqo1qmsYZK+rZN7Hw70tuMQJWxePzaXOyiBzk8tV8kDXHq4bxm5i7yGqn/RuauvXEEEUXD+ZI7G1ZUe0kN+thAHXDAqlMPd+Qr7DjW/BoZuwtQ63eMPeHgOlP/Z85lY5GFS7kF2kdNE9k0EqUwVXolJoN2ZbncETos9WLxGPba3wQ4iE5FPHjTdyOMvCKel/o7Zlkb8A42LFHl6h/YbOdn17ntH7UGq7QsO/KM1KEuvvoonOJGPy7GKTk2jil376UrB5L9QCDOd54HMssiEu7d+1LlDJcP7Uw9WwQ4QSWrWGgVuLDWKSrvB4l1ETsXZCHLKZJKPrsj05mXBNLsZQdSIRhDhFGq5CsXKCLnrUtkxWY6yZRyaM74yHtdgkXiUSGwqENOZPbpTqSbHXr7Qj9q5YfeBv3+3ODf0V6+8MY16c1vJgjiBft1qSicInk+t7ml50dOOF5YSUdRQu18yyhfMoIhaK+9+ljoN6xUNdd9/z8DDvc/cEUJd2pcKQ/HCIb40BcnLIXeb3U1GgjPBiKC5Qjax UoqtoWYk 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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: On 4/16/23 22:33, Andrew Morton wrote: > > Circling back to this fix... > > The BUG() is obviously real. We're unsure that Ivan's fix is the best > one. We haven't identified a Fixes:, and as this report is against the 6.2 > kernel, a cc:stable will be needed. > > According to the sysbot bisection > (https://syzkaller.appspot.com/bug?id=7d6bb3760e026ece7524500fe44fb024a0e959fc), > this is present in linux-5.19, so it might predate Zach's > 58ac9a8993a13ebc changes. But that bisection claim might be > misleading. > > And Zach is offline for a few months. So can people please take a look > and see if we can get this wrapped up? > > Matthew, the assertion failure is in the > > VM_BUG_ON(index != xas.xa_index); > > which was added in 77da9389b9d5f, so perhaps you could take a look? > > Thanks. I tested the reproducers on the 99cb0dbd47a15 commit, and they do not trigger the problematic condition of shared memory truncation or hole-punching. I will investigate further, as there have been many changes in khugepaged since the 99cb0dbd47a15 commit that could potentially affect its behavior.