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Fri, 26 Jan 2024 09:31:37 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Chenyuan Yang Date: Fri, 26 Jan 2024 11:31:26 -0600 Message-ID: Subject: Re: [Linux Kernel Bug][mm/gup] 3 Warning Crashes: kmalloc bug in gup_test_ioctl, is_valid_gup_args, pin_user_pages_fast To: Matthew Wilcox Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzkaller@googlegroups.com, Zijie Zhao , John Hubbard Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 974F220023 X-Stat-Signature: j6jykxj6hcu6cusc6urref33sqb33id5 X-HE-Tag: 1706290298-438085 X-HE-Meta: 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 WiHIZBc2 800b3G52LGuIfWp8otUZADlPmEVcnB0ozOvoNTqABp7dako6lnPke5yzESd5kSNlJJo6Xk7h5m4kSZb+YBo5pxe5V8El1BDIGLllQsAsvCkN5b6IpKUBClq5ZXeWv0pHcMd7lxBHEnpte1a6YM89CPcNalZHnzuMw6p4gxmWQo67xAHYsxsubPmOy7ab4ftk87pXMoauHni5bYFdsqBdgwmvmHKHYfOTvijrN+N2cFoC9SfB2o6sB9OqULtqu4DVDOeqz1yezqaAuvlTiw1Je0MPumBzVX0w9iQMGjf/eaatdHEi78GpJRrMUXEdx5xaoQ4LryUk8r8eHGN0z5GBNDkOW25vnp2i4cFKUIQXx4MgXGcLMH2nCEqmvDlJf6TqSIz0sC0j21g3GFAa39pK6JjigpeA+OZ7ncdgtSg5ToiTnfECuqgifw6xaXWkdr19m+nL06K1jodc0l1o= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000705, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello Matthew, Thanks very much for your prompt response! For `gup_test_ioctl`, we generate the descriptions for it for interaction and testing: ``` openat$gup_test(fd const[AT_FDCWD], file ptr[in, string["/sys/kernel/debug/gup_test"]], flags const[O_RDWR], mode const[0]) fd_gup_test ioctl$PIN_FAST_BENCHMARK(fd fd_gup_test, cmd const[PIN_FAST_BENCHMARK], arg ptr[inout, gup_test]) ... gup_test { ... gup_flags int32 ... } ``` In this context, I would like to seek your valued opinion. Do you believe it would be more prudent to avoid fuzz testing the `gup_test_ioctl`, or are the warnings in `gup_test_ioctl` an anticipated outcome? It seems that `gup_test_ioctl` can indeed be exposed in the kernel by accessing /sys/kernel/debug/gup_test. Thank you once again for your time and expertise. Best, Chenyuan On Fri, Jan 26, 2024 at 11:11=E2=80=AFAM Matthew Wilcox wrote: > > On Fri, Jan 26, 2024 at 11:04:53AM -0600, Chenyuan Yang wrote: > > Dear Developers for Linux Memory Management, > > > > We encountered 3 warning crashes when testing the memory management > > with Syzkaller and our generated specifications: > > These all come in through gup_test_ioctl(). It's my impression > that this is something you can enable to wreak havoc on your kernel > and it's not something which should ever be exposed to fuzzers. > > > > >