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Tue, 01 Sep 2026 04:53:03 -0700 (PDT) From: Guilherme Giacomo Simoes To: ljs@kernel.org Cc: akpm@linux-foundation.org, david@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, liam@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, pfalcato@suse.de, riel@surriel.com, rppt@kernel.org, surenb@google.com, syzbot+395b7abe9696862fc188@syzkaller.appspotmail.com, trintaeoitogc@gmail.com, vbabka@kernel.org, willy@infradead.org Subject: Re: [PATCH] mm: fix the race on huge alloc failed Date: Tue, 1 Sep 2026 08:52:48 -0300 Message-ID: <20260901115248.26650-1-trintaeoitogc@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: C3B2C16000B X-Stat-Signature: as84uim79gy69gaqd9ufktg3a5e3c6zn X-Rspam-User: X-HE-Tag: 1788263587-612197 X-HE-Meta: U2FsdGVkX1+FGRkmzo0s/GHoFEux1ZgHPJriKUo4XR/s6iNOF5GWIhzJ0SYn0MCcDZ/ymU+X8DdXCrFiM8vD7MhcHTf1RXQ22JE+EL933bedqiqxRNdphuY0sjkGXh+ZAdLAIK/l42C6pDoym/7rHroXqPYm9aQX//o/8j/JOwGDuLMZwY+lukN+U1bRUJtjyInqFMr8OXyqc46qvhofVgSn43ROEF2t9cYaquOIEJfOC+c93i+J/8e8/677rLDQaQp/oiHx0mHS+lDtkygMhu0njVHMRgwY5LG0rJxS2Ruq8stMCV7hKkTSGqMfGrpLdAirXhI3QTC0X6RniDX3NjBJLv5YGiBvf5AvnxBaoNZ2wxMQ7tghOMb27deaxgahqtIcKr/8SBLnH7OzeorjShbfPrmzf7UkZByqMtTrE8zm/ALb2ExcgmUGandhZ6kBzWos8zjPx3s6AD4C/Iti6qg84ff2MLlcebPMrXXuoxhv6kBXgu5OmRGivuD151Hc1MT9lY0b3O56zYy0RIikN3K3WFzG/nYMTYTal2n/iqzLMNIQqo7aluS2cP085HGNsScomKGY807AEYJz0oqFjckA8MSz9JPtNZtYaBXQLilsxtRShDklXyVnspwgZwt3qEA4o7cYyU0nyl6aa6bQ735YMeCogl1+PzcGP7ASBI6CCqjjdyGGJktRS9SXE7ib6NcxGvr31dIyOZOOEmKyrnNuMKBCuZhmb6Rhr218MxJ9fhKsUGPxhJdEIxlfbC4oQ5SFkepzJHKc711HiLJe7BXXqpICXhO6F66zCWrUqGJhL6LAN6zhkNgvZkl0T5tkoNMHik9IOmdPWjMUWjLSUBE89T3m1K4euRHUFVECWhDvjtyhcdQsltMtSuhZMe/VVgLJVAXrwk5oQ+akgOUgT+EDhtGEAYYRLlVUUKe2b5bc9zzf7vSx+yKofAd5Oh6rTlYsbQ8JsRrPXV3z5FS CwCDxQcR 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: First, thanks Lorenzo to help me with this... "Lorenzo Stoakes (ARM)" wrote: > > > > I don't think it's enough to just add a data_race() to this one read of > > > > vma->anon_vma. I think it's quite prevalent. There's probably other > > > > syzbot reports that mention it. > > > > It sounds to me like the most cromulent solution is simply adding a > > > > /* maybe vma_has_anon? */ > > static inline bool vma_has_anon_vma(const struct vm_area_struct *vma) > > { > > return data_race(vma->anon_vma); > > } > > > > and churn everything to use it. > > I'd prefer vma_is_faulted(). That'll align better with my scalable CoW work > also. > > Anyway I agree with Pedro that a data_race() resolution is appropriate here > rather than an unnecessary READ_ONCE()/WRITE_ONCE() pair. Okay, if only a data_race(...) is enough to silently KCSAN, I can send a new PATCH or send a v2 of this PATCH with this new implementation and with a fix of commit message