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Thu, 4 Jul 2024 22:21:50 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: Date: Thu, 4 Jul 2024 22:21:50 +0900 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] possible deadlock in __mmap_lock_do_trace_released To: Axel Rasmussen Cc: syzbot+16b6ab88e66b34d09014@syzkaller.appspotmail.com, syzkaller-bugs , linux-mm , Andrew Morton , LKML , bpf , nsaenz@amazon.com References: <0000000000002be09b061c483ea1@google.com> <98dcfbda-6237-4bf6-bc66-6f31cf12f678@I-love.SAKURA.ne.jp> Content-Language: en-US From: Tetsuo Handa In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 6CC7412000C X-Stat-Signature: xqpiiaifah7a565zqymg6xkeycm5rdw8 X-HE-Tag: 1720099334-214619 X-HE-Meta: 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 kkEmftAR ZWon7uCnHevKKdA5oeVJ3ewZwMQ6WSF3JlGbgTpJmWCsmiAR1KlH6uUGlMlnCboDhFA0O5hy7hY+4wg1sE/PKq/VGObXgu64S+KQSI5XXcqT/lEM7GUMd5F0jOZzTyUwO8Lg0NjpmyhLYFKHToxP4LiQgHm64RSMMn5mh3jv7qg+cQUw+49lpwNLGz0QzBRHIPnuMOBJbFCO3fqoycuDi8MeI2Tea/+CBXaNRXcCfe1hgrfO6pqfPhCocuh/vutPprbxrfGEEoIl2jHsa7mFT8gurzZphkWojft27l29l5Fhx1be2XQ0h0VYMuzQ+wE2j2vYXCQh/YJtBLg/gRluiiJvjkkx70VYLAV5iXn/VZCiTOaaVq7opsYCfnH/1Iw7klIApoGOeXSkCuhVPnr574EJE7HKwCcsgrITiYAjaF/Q8XO3Qf9ouluqy3GWTI7ZK16Jft64BIab3Wtc= 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 2024/07/03 7:35, Axel Rasmussen wrote: > But, note that stack_map_get_build_id calls mmap_read_trylock, so I > would expect in the recursive case that call will simply fail, and > then stack_map_get_build_id_offset appears to deal gracefully with > that? Unless that mmap was already held for write (or someone has started waiting to hold it for write), recursive mmap_read_trylock() will succeed. Thus, unless there is a guarantee of no infinite recursion, we should implement a safeguard based on the worst scenario.