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AJvYcCW2kLXPj7T6WxxhiXloIz3zbPvkRvZzwRUCEsEoYACzvjlK46N/3DVlH6xja5GDcnJD8dDVCN4mMQ==@kvack.org X-Gm-Message-State: AOJu0YyfnNcpmh2lgoR35yIx7Vsj55paixRx6BJYpMbgDHas0Kn2VG77 u+AFUdnR9gl3C9sKxTJccwHISI1Y1hqB+Qt24q1wE8szO1ASBSFtOHkhPPMD1l3j0OKAo3nTUAy 1Az22bSBfDQhznVzhUK2bFuB21Yy/m66HZAcNY4g/ X-Gm-Gg: ASbGncsRVaYiz59adpqeB/qx7Q/qp9ZhUxDyRwMw1Ca9beIsZ9GWqHcGC5DJWI5X14/ hSY3taSwTGNiRemFNcNW9Ea+D2kEyMyiMvDJ5xBcqCUO8bgoYvsuxjxTybKtPrd8PdS0oZlr2W9 GSLtZMyMTYqcSjEGwSv9M4XAWOi4TeHl8buYUehjTqLgYofSIfpdedBBx+RPNWX1Y6uVuyd5azc PUj8awwaHpROadB4+ggJadYaM3UJrMnVqA= X-Google-Smtp-Source: AGHT+IEyXGTWR0XZZte/eASlEm7qrI06sVh3iGjpWdMzm8/vWVFxkQtUydmt9xCTl4XoHoqeljjoWTaB4r+v4tgfXVM= X-Received: by 2002:a05:6402:290e:b0:60e:5391:a9e5 with SMTP id 4fb4d7f45d1cf-614c50e54camr10227a12.5.1753300876951; Wed, 23 Jul 2025 13:01:16 -0700 (PDT) MIME-Version: 1.0 References: <16c97e30-19c9-41e8-b73b-c0b3c8eceff3@suse.cz> <28e1fc65-995c-4185-b5c2-7eb001312698@lucifer.local> In-Reply-To: From: Jann Horn Date: Wed, 23 Jul 2025 22:00:40 +0200 X-Gm-Features: Ac12FXw7CgyRl7JjB9ySJ0F_t8x_hAcLmfJ4tfnYlheNfb0W0Wn0LvVOrf4lVAk Message-ID: Subject: Re: [BUG] hard-to-hit mm_struct UAF due to insufficiently careful vma_refcount_put() wrt SLAB_TYPESAFE_BY_RCU To: Lorenzo Stoakes Cc: Vlastimil Babka , Andrew Morton , "Liam R. Howlett" , Suren Baghdasaryan , Pedro Falcato , Linux-MM , kernel list Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6FA6BA0005 X-Stat-Signature: 8x8hr1168585od3ubuzdbzggbo9o7u5f X-HE-Tag: 1753300879-579184 X-HE-Meta: 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 sh0JIny/ 9vvgvGCH39qQxIKfrR2PYxsojuaERBptyzVmKW1Wp2BGVlu2tpMTyh4ItAs25i/9IUS43qS6LDchYVbofNAmV62B0JuaEHzsSyw/fKUdXzD8HMGUki9pclS1BXnH4NMS203iafywcVZ0aj1EsPHrjC5jrvuOTcZYdnW4glMOhGgkZmOiWOH/M7o46mbqi/+ocZX8wKE/tn6v3hCWAr4gSG4UKNvY/mTYzgvYmiXopFFXtlSIkDR84n4geX1xjiVr/0n4k+Zv65EKtwVc= 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 Wed, Jul 23, 2025 at 9:52=E2=80=AFPM Jann Horn wrote: > I'm not sure if I'm understanding you correctly; but yes, > __vma_enter_locked() waits for all the waiters to drop their > "refcounts". (It's not really a refcount, you can also think of it as > a sleepable read-write lock where the low bits are the number of > readers.) Sorry, that's not entirely true, since an attached VMA has a refcount elevated by one. It's kind of a refcount, and kind of forms part of a sleepable read-write lock, it's complicated.