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AJvYcCVCS0Rlhbrmky8uqBRq9WOhCoIZZ6sAQNlMngE7r8D4rvgM6y+Pa5EHDqYJyLcElvnfg/YndbhudA==@kvack.org X-Gm-Message-State: AOJu0YzBBgQuRgOvaL7RsNJi4MnVWaVF3/n9tuDKajP4yVd4r0RAw3PT xQ1bCvBVPY+ILf5+tMBgPxl8gnRd3aMLY5/CCN9om4koIWGdVJ9v+Znt6XjwRkQ5fAZsOOFgBaD Q6ILARMzcg98DJ2EvPKVsJn8RcDO95zw= X-Gm-Gg: ASbGncurg7jIJRyV0LJ8MRC6kPhLchm2cwtcdFxoPs9y2YDILg8e1frX1ZU2ce0S5IH 2MzsQeBWjx0mAJiSEI4JmYGr3sz2f1ZA0wi+1Qp7XXOQcwaSTRIoAo5R/cGeuq0ycj17UCyC6NJ PAru1hcONVlZtzWsSpLiO+82h4KrPgRIa41PHUALPgZjciuMiWYJ7NSnJTNPMb51VE6xSxfochF Hlaj029dvQ1nEOLIgHlx2EXrOv+ X-Google-Smtp-Source: AGHT+IHHntWNeb6307IeM+SI0zlh8EZ/o4DFwzv5FzECn4t5M558pYaWqyhZ8DpdAmPb1hEuATGnTdzfcm3dZ2CLfJQ= X-Received: by 2002:a17:90b:3148:b0:327:5360:5b1a with SMTP id 98e67ed59e1d1-3281570ba17mr17428904a91.37.1756819204596; Tue, 02 Sep 2025 06:20:04 -0700 (PDT) MIME-Version: 1.0 References: <20250826205617.1032945-1-vishal.moola@gmail.com> <20250826205617.1032945-8-vishal.moola@gmail.com> <5ee2b684-94d9-40be-b01c-b0538ced33bc@redhat.com> <20250830074747-mutt-send-email-mst@kernel.org> In-Reply-To: <20250830074747-mutt-send-email-mst@kernel.org> From: Stephen Smalley Date: Tue, 2 Sep 2025 09:19:53 -0400 X-Gm-Features: Ac12FXzjdgirVSRxrRZeOJriOnHYQBVpd6gTvQBDolPhv7jSSxNDmD9GjD6pYDQ Message-ID: Subject: Re: [PATCH v2 7/7] virtio_balloon: Stop calling page_address() in free_pages() To: "Michael S. Tsirkin" Cc: Matthew Wilcox , "Vishal Moola (Oracle)" , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Paul Moore , Ondrej Mosnacek , selinux@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 57F0F120011 X-Stat-Signature: dz5rz5kseoutchz6azrdmn5iz6imo1t7 X-Rspam-User: X-HE-Tag: 1756819207-822632 X-HE-Meta: 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 YJ/VotQr 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 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 Sat, Aug 30, 2025 at 7:48=E2=80=AFAM Michael S. Tsirkin = wrote: > > On Thu, Aug 28, 2025 at 03:53:56PM +0100, Matthew Wilcox wrote: > > On Wed, Aug 27, 2025 at 11:29:22AM -0700, Vishal Moola (Oracle) wrote: > > > I imagine theres more of these lingering in the kernel, but theres so > > > many callers and I only looked for the ones that were calling > > > page_address() inline :(. > > > > There's only 841 callers of free_page() and free_pages()! > > > > It's a bit of a disease we have, to be honest, Almost all of > > them should be using kmalloc() instead. To pick on one at random, > > sel_read_bool() in security/selinux/selinuxfs.c is the implementation > > of read() for some file in selinux. All it's trying to do is output tw= o > > numbers, so it allocates an entire page of memory, prints two numbers > > to it (while being VERY CAREFUL not to overflow the buffer!) and copies > > the buffer to userspace. > > > > It should just use kmalloc. > > Why even kmalloc? Why not have a small array on stack? Patch posted at https://lore.kernel.org/selinux/20250902131107.13509-2-stephen.smalley.work= @gmail.com/T/#u > > > Oh, and it should avoid leaking the buffer > > if security_get_bool_value() returns an error.