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([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id T+qcHPdh0WP1JAAAMHmgww (envelope-from ); Wed, 25 Jan 2023 17:08:07 +0000 Date: Wed, 25 Jan 2023 18:08:06 +0100 From: Michal Hocko To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, hughlynch@google.com, 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linux-perf-users@vger.kernel.org, kasan-dev@googlegroups.com, selinux@vger.kernel.org, alsa-devel@alsa-project.org, kernel-team@android.com Subject: Re: [PATCH v2 4/6] mm: replace vma->vm_flags indirect modification in ksm_madvise Message-ID: References: <20230125083851.27759-1-surenb@google.com> <20230125083851.27759-5-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 3AAA04000C X-Stat-Signature: 8mfekk84ow67a8r1w7nwi1ccd7o8yad1 X-Rspam-User: X-HE-Tag: 1674666488-425361 X-HE-Meta: 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o6htzLqOE/ddACl1eAQMUcggK1ycwJ0JMVi5sYvWk8jSEBX5c8kpc51I1e/2TTK+9et0YEaSv7QM3ERz0kNyTeZWZRyu7EJLM/BHXKXuQXJkajTiOTcW45zJ3U0Mzit6v0VZmn7lr0/8Z1ccHKWAYTw+XvOx+kCVAiv+AxNuCDPTX8P+7qaIRdpNYzGPNchtRgVpxPr6tdQdmelJHNrMIb1nG5d37i/udvMlM98DANCm55k5x24W+8coKmR00MQ86eVm/UOFruHdGZGKT4zv3uOlP11mzDFS8Tj5oxJUFGjNFckXScYKJDHP39caIw6jvHroXNG4kclzxgnMBJnCRs0adk5i0RNDUvMkY8HUR+yDQ+Jgkk0tga2fQoSovHe/ZhAa3Pct81j/PzYQj9ktI4 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 Wed 25-01-23 08:57:48, Suren Baghdasaryan wrote: > On Wed, Jan 25, 2023 at 1:38 AM 'Michal Hocko' via kernel-team > wrote: > > > > On Wed 25-01-23 00:38:49, Suren Baghdasaryan wrote: > > > Replace indirect modifications to vma->vm_flags with calls to modifier > > > functions to be able to track flag changes and to keep vma locking > > > correctness. Add a BUG_ON check in ksm_madvise() to catch indirect > > > vm_flags modification attempts. > > > > Those BUG_ONs scream to much IMHO. KSM is an MM internal code so I > > gueess we should be willing to trust it. > > Yes, but I really want to prevent an indirect misuse since it was not > easy to find these. If you feel strongly about it I will remove them > or if you have a better suggestion I'm all for it. You can avoid that by making flags inaccesible directly, right? -- Michal Hocko SUSE Labs