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(dynamic-2a00-1028-838d-271e-8e3b-4aff-fe4c-a100.ipv6.o2.cz. [2a00:1028:838d:271e:8e3b:4aff:fe4c:a100]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49059cc9a91sm48939425e9.1.2026.05.25.09.19.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 May 2026 09:19:22 -0700 (PDT) Message-ID: Date: Mon, 25 May 2026 18:19:19 +0200 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 06/11] moduleparam: Add seq_buf-based .get callback alongside .get_str To: Kees Cook Cc: Luis Chamberlain , Pengpeng Hou , Richard Weinberger , Anton Ivanov , Johannes Berg , "Rafael J. Wysocki" , Len Brown , Corey Minyard , Gabriel Somlo , "Michael S. Tsirkin" , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Bart Van Assche , Jason Gunthorpe , Leon Romanovsky , Laurent Pinchart , Hans de Goede , Mauro Carvalho Chehab , Bjorn Helgaas , Hannes Reinecke , "James E.J. Bottomley" , "Martin K. Petersen" , Daniel Lezcano , Zhang Rui , Lukasz Luba , Greg Kroah-Hartman , Jiri Slaby , Alan Stern , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Jason Baron , Jim Cromie , Tiwei Bie , Benjamin Berg , =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= , "David E. Box" , "Maciej W. Rozycki" , Srinivas Pandruvada , Peter Zijlstra , Heiko Carstens , Vasily Gorbik , Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Vinod Koul , Frank Li , Daniel Gomez , Sami Tolvanen , Aaron Tomlin , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrew Morton , John Johansen , Paul Moore , James Morris , "Serge E. Hallyn" , Andy Shevchenko , Georgia Garcia , kvm@vger.kernel.org, dmaengine@vger.kernel.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org, linux-um@lists.infradead.org, linux-acpi@vger.kernel.org, openipmi-developer@lists.sourceforge.net, qemu-devel@nongnu.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-pci@vger.kernel.org, linux-scsi@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, usb-storage@lists.one-eyed-alien.net, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-hardening@vger.kernel.org References: <20260521133315.work.845-kees@kernel.org> <20260521133326.2465264-6-kees@kernel.org> Content-Language: en-US From: Petr Pavlu In-Reply-To: <20260521133326.2465264-6-kees@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/21/26 3:33 PM, Kees Cook wrote: > Add a new struct kernel_param_ops::get callback whose signature > takes a struct seq_buf instead of a raw char buffer: > > int (*get)(struct seq_buf *sb, const struct kernel_param *kp); > > The previously-legacy .get field is now .get_str (char *buffer); > .get is the new seq_buf-aware form. param_attr_show() prefers .get > when set, otherwise falls back to .get_str. WARN_ON_ONCE() if both > are set. Return contract for .get: > > < 0 : errno propagated to userspace; seq_buf contents discarded > = 0 : success; length derived from seq_buf_used() > > 0 : forbidden; the dispatcher WARN_ON_ONCE()s and treats as 0 > > The default policy on seq_buf_has_overflowed() is silent truncation, > matching scnprintf()/sysfs_emit() behaviour. Callbacks that want a > specific overflow errno can check seq_buf_has_overflowed() and > return their preferred error. > > No callbacks use .get yet; the legacy path is still the only one in use > after this commit. A subsequent commit teaches DEFINE_KERNEL_PARAM_OPS > to route initializers by type. > > Signed-off-by: Kees Cook Reviewed-by: Petr Pavlu -- Petr