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Tue, 10 Jun 2025 23:15:37 -0700 (PDT) Date: Wed, 11 Jun 2025 06:15:37 +0000 From: Wei Yang To: Andrew Morton Cc: Wei Yang , Liam.Howlett@oracle.com, willy@infradead.org, maple-tree@lists.infradead.org, linux-mm@kvack.org Subject: Re: [Patch v3 0/3] maple_tree: Fix the replacement of a root leaf node Message-ID: <20250611061537.5sphqxawrrhwz74h@master> Reply-To: Wei Yang References: <20250611011253.19515-1-richard.weiyang@gmail.com> <20250610183727.5116056fe4cb7ccd36e93b9d@linux-foundation.org> <20250611025436.wa37ileuswr5gleg@master> <20250610205539.75dc8db5fc245510228bcbf8@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250610205539.75dc8db5fc245510228bcbf8@linux-foundation.org> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 2F28D1C0009 X-Stat-Signature: 9moxepwfrnsyfhxp7apuepjcjtg9rnqo X-Rspam-User: X-HE-Tag: 1749622539-844927 X-HE-Meta: U2FsdGVkX1+yG+iKTqU6Ehbqf41y9aN0P9ApllFOPPCQZuOchzmZmE2usZfMLl09mB6XbOw5d1CXuxqJB1847lVI1jwxiH+lPafzH8dGfkyQuW30L7hyN2cAPJm/13d1NDG/cItWp/lpnMmNXwRVkanpfBBNOvrcEaysyHutuV7foxRWhJqCv2hv6hQwtN9xo+GboLUNFvnuiMGuBEDa9Jrzzn0F42oVZBYvyrNFCg37fgIckgTjTe69TbIGMXT3HlTnGRqSe5XP3e6S66UgCA6ICFU5DIqB3POCSFiv117f9e9qlaB/0uhByCckw9Y7OvDzxMlWv+Imvnp2kWaWGQdQL/cuywSXaO+LlFrgD873tHUwo3yP1wWqz307qH5UHLmVVaelvGcGMI96xoOccBe9B8fkel33pnxCFxyztJnEYGBZccWca/T3SuF9f+ivD0l1BYMEwmuDGWYeMgc5BpdUyhilDgsFnUB0fGkY0igPCkmTvN4sKVF20T0khH7/5qPvm4uV+oTdfkFhocPvTQTYqOckECN9aZtE8GyQ1LwpJqHdejfLTgeV1lrwW1jM0E7U633SngCsn1XKc5EG0hfvfZyaxpwl5lzWtbb0zZjW53ZwfPoEKBucz8th1wEBTkAqAXiiBM6l//8QShr+qNBl20dmVjlsdsTWWFG7RG6lcsIMvZlKhb+luywg4m0/n+Z0kauqM5+hP1tRk6Y17gHEOZxNy0NbvteoWDLYkKA7/kBqkPxCd+zPOBZXmiR7/phQ3ayEdvF/54zvaoCBET6MulDaFtxpRxUjY+e2A4QYD9JJdn4uOpFbCoQ4wF/F1MWqxo4CM3TKJaQrndIZYuvg87/lB1sEr+gMWliuNGk4GHOtsYcKVlX7sJXYzP6vHpq86/R/blPyyF/abcLKM1/jvZCxEcsVcRSZ/acAjvkqJwf62+d3aIvDzNA/bs3NdJwxEEyexgnuvC1yj8u Byxbuu2y 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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 Tue, Jun 10, 2025 at 08:55:39PM -0700, Andrew Morton wrote: >On Wed, 11 Jun 2025 02:54:36 +0000 Wei Yang wrote: > >> On Tue, Jun 10, 2025 at 06:37:27PM -0700, Andrew Morton wrote: >> >On Wed, 11 Jun 2025 01:12:50 +0000 Wei Yang wrote: >> > >> >> On destroy we should set each node dead. But current >> >> code miss this when the maple tree has only the root node. >> >> >> >> The reason is mt_destroy_walk() leverage mte_destroy_descend() to set >> >> node dead, but this is skipped since the only root node is a leaf. >> > >> >Thanks. You added cc:stable to two of the patches and that's great, >> >thanks for remembering. But the changelogs didn't tell us why you made >> >this choice. >> > >> >So, as always, please always describe the userspace-visible impact of a >> >bug when fixing that bug! >> >> Thanks for reminding. >> >> Do you prefer to have a new version with the description in changelog? > >No, that's fine - please just send it in reply to this email. Below is my understanding about the impact of the bug. --- Without the fix, maple tree user may see old value after overwriting the whole range [0, ULONG_MAX] on a tree containing just one leaf node. If it happens, kernel may access some invalid data and be crashed. Since we rarely overwrite the whole range of a maple tree, we don't expect it to have userspace-visible impact in practise. -- Wei Yang Help you, Help me