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b=rpcqoDlKTU1jsbrQNie44i4xKe6rjvUvREyH7QEom9u5llG1YAo4JQg3XggqsD7Mx U8omtI5x7whVocUqSygiRoV8Wk3oVscaYZ/AGDPhOymsQRArRJVX8Nh0p3/cLW82oP wCVF38QB159d0GPbST+mgglRfeBRMOUiYvALfm6Gn5Zvo6ePzy8PmYyo8s5061GvFo wsWzn9Vvsg+MFKf9ONxnpiUlV31qr6sDj4yueynHEEg1twOaG3I65JsnRncLVI7hdf +R0rP8i588nEN/4pQ0jtqIl/09ps0K1GK81+XTsVioX1Hsx4U8yr/ZW8yJLfQ+YLzq 5RKS47HfVQyqg== Date: Wed, 04 Dec 2024 14:43:54 +1000 From: Kees Cook To: Matthew Wilcox , Uladzislau Rezki CC: Kefeng Wang , zuoze , gustavoars@kernel.org, akpm@linux-foundation.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, keescook@chromium.org Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_-next=5D_mm=3A_usercopy=3A_add_a_debu?= =?US-ASCII?Q?gfs_interface_to_bypass_the_vmalloc_check=2E?= User-Agent: K-9 Mail for Android In-Reply-To: References: <57f9eca2-effc-3a9f-932b-fd37ae6d0f87@huawei.com> <92768fc4-4fe0-f74a-d61c-dde0eb64e2c0@huawei.com> <76995749-1c2e-4f78-9aac-a4bff4b8097f@huawei.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 95D942000D X-Rspam-User: X-Stat-Signature: 1b86wez8ktt7be9h688ur7pwmhu955ia X-HE-Tag: 1733287429-906638 X-HE-Meta: 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 H+0YpuAf NFkEKwD4B1r/E4APdFGjnIRHwVPgSymCki3GDUlpdEndnAud01QbiZqMSxUULNtokghCcu5iQMpTpXYgybOJJ0ku3s+8YfEOlF9d9hGwm8Uf9pf7zLC5OpSynYAPQYPqocJ+GMTIY1flhbaxJWIcBU8oOW8M5nmVUvxrruHTFYAWRlarCh9dX6r6CZN6jutOg9FzucYAOL59fDTk8EJaSzMjxhS3HzTOM080lya5+c7EI0wb52PMa0aBYlejAk4EXntIwmszhDPSebVT6aijerhHPxZ591jgglq3corOQ0L7YbfkxmZ6eKg9goI+2TKNM9pyxFCxFwALdRbPksMTqvo5rbA== 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 December 4, 2024 5:56:34 AM GMT+10:00, Matthew Wilcox wrote: >On Tue, Dec 03, 2024 at 08:02:26PM +0100, Uladzislau Rezki wrote: > >I think there are a few other things we can try here=2E > >First, if the copy is small (and I still don't have an answer to that >=2E=2E=2E), we can skip the vmalloc lookup if the copy doesn't cross a pa= ge >boundary=2E Yeah, this seems a reasonable optimization=2E >Anyway, NACK to the original patch; that's just a horrible idea=2E Right, please no debugfs knob=2E The point is to make sure the check canno= t be disabled at runtime and to make the check a no-op=2E Please use the bo= ot param to disable this check=2E=20 -Kees --=20 Kees Cook