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[209.85.208.47]) by smtp.gmail.com with ESMTPSA id ce23-20020a170906b25700b009920f18a5f0sm9733214ejb.185.2023.07.04.09.40.05 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Jul 2023 09:40:05 -0700 (PDT) Received: by mail-ed1-f47.google.com with SMTP id 4fb4d7f45d1cf-51d7f4c1cfeso6819313a12.0 for ; Tue, 04 Jul 2023 09:40:05 -0700 (PDT) X-Received: by 2002:aa7:df17:0:b0:51d:d568:fa4e with SMTP id c23-20020aa7df17000000b0051dd568fa4emr9181443edy.41.1688488805133; Tue, 04 Jul 2023 09:40:05 -0700 (PDT) MIME-Version: 1.0 References: <000000000000b73abf05ffa60902@google.com> <20230704092451.72974b7a62ae08d48c077e10@linux-foundation.org> In-Reply-To: <20230704092451.72974b7a62ae08d48c077e10@linux-foundation.org> From: Linus Torvalds Date: Tue, 4 Jul 2023 09:39:48 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [syzbot] [mm?] WARNING in __gup_longterm_locked To: Andrew Morton Cc: syzbot , linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A5DF714001A X-Stat-Signature: finuaswk8u1ftm66o9i5q6wwi5ncnmw5 X-Rspam-User: X-HE-Tag: 1688488808-59979 X-HE-Meta: U2FsdGVkX1/hgHovwELFp5VcV9WIBI/AvORNCIqTKbnHrp1bMBVOpsc/hIs+M6EQ6Q8aVGJkifBMfNGHuGn7Qm0nfGU9p21PUjei8gZxSZqSnMBekrtQ84OiQ1zV3izo6SE/hnArAFT51LUYsp5CcKcPizi96sxgzWT4J0dw0YU8oe5bxr4TGdoAT6Z22YAK+DK7EMpmhuw+hvzhZiqoWEE6oMGidqI02dFdkAbD5I/BLvo1gEUK2hW2MeCzIS4CTcm55xqCXn2Aw36HYcViP2zx3wkope5ah59v7tQor/aef0xOFNkTxoYjgzZqC6HvAgnexA76VwJPWPqTp9KBlaNE+RxYB+iycFEYHya3boaxic6DvDkK5NUDOyfSUmBvQVWc4fB/0KJzT1tbRw9DnVCcUCUPU1HerKjCXid8oBwyWrBIQI7EJ0nBDoisbFyY4ln5Py20h2/Qm9eGigbL2kXjsAvxQNvE4hjSknW1mpF3GMORDgHDQRwkWjUORC5ohUjR+EYeFsIVOVu1/CToqG6yewbaPyMqmYSpRj4faKNAwC5JsYyjYEimEjUvPHjf/yMqiZJWJXYFK9DFFezNMVowOVaHY42VhwWGXOtvLM+Lxu5MqyEfMnuTJj5ztDjOmAAE2+FBS+zVHLuPwKR6r+sZQ502W94pGX+LMbBHP9HYJPaCswjSUpnvNseFY3YNuIaH4ePyt0CIkDZ/Nj9q8hMXS6sX1kwhmrVXc0IvEllgPTOLb+t1LNx5IV+L3wG8LTZ0sMNLEAbpXVciSZnnq7mczC9w72ydHS2A22vLktZvFTBgqW2cdcVJeJSm+L6KOUrzoeLjDM0oXIllbw7ZhaPqPZ8J1PZGiO49CkwoEJ4ABAkjszhoTSqLrWCchry2SvrEso+OtI9qJwneDg5V13TJuEZ2KjFnt8ketXPlVwtaWB7y3R5YsxZHTbt4oDlvaL1QWhd3Uxyc5rwIPj4 5xqjKNtM 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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 Tue, 4 Jul 2023 at 09:24, Andrew Morton wrote: > > Thanks. This is the temporary warning which was added by Linus's > a425ac5365f6cb3cc4 ("gup: add warning if some caller would seem to want > stack expansion"). Yes, and the randomizer system calls aren't very interesting for that warning. I don't have any good idea for how to distinguish "this is a randomizer that is just doing crazy things by its very nature and is passing in nonsensical system call arguments" from "this is a real application that is doing crazy things that we will sadly have to try to be backwards compatible with". And at the same time, I _really_ don't want that warning to then perhaps hide some *other* more real warning from the test automation. End result: I'd love for that warning to trigger on real applications (including ones run by any cloud test infrastructure, although I doubt that infrastructure necessarily runs very interesting loads), but not on things like syzbot and trinity that just randomize system calls. Does anybody have any ideas how to tell them apart? Maybe syzbot already sets some flag for this purpose that I just haven't thought of? Linus