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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49035ecac15sm31613075e9.6.2026.05.21.09.46.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 May 2026 09:46:34 -0700 (PDT) Date: Thu, 21 May 2026 17:46:31 +0100 From: David Laight To: Kees Cook Cc: Luis Chamberlain , Pengpeng Hou , stable@vger.kernel.org, Petr Pavlu , 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 , Eugenio =?UTF-8?B?UMOpcmV6?= , Jason Baron , Jim Cromie , Tiwei Bie , Benjamin Berg , Ilpo =?UTF-8?B?SsOkcnZpbmVu?= , "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 Subject: Re: [PATCH 01/11] params: bound array element output to the caller's page buffer Message-ID: <20260521174631.71a06440@pumpkin> In-Reply-To: <20260521133326.2465264-1-kees@kernel.org> References: <20260521133315.work.845-kees@kernel.org> <20260521133326.2465264-1-kees@kernel.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: b4ojd9rcfqoc8iux1bzr378m8e9oru7y X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: ED4CA20007 X-HE-Tag: 1779381996-223488 X-HE-Meta: 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 kdhoHw8M 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 21 May 2026 06:33:14 -0700 Kees Cook wrote: > From: Pengpeng Hou > > param_array_get() appends each element's string representation into the > shared sysfs page buffer by passing buffer + off to the element getter. > > That works for getters that only write a small bounded string, but > param_get_charp() and similar helpers format against PAGE_SIZE from the > pointer they receive. Once off is non-zero, an element getter can > therefore write past the end of the original sysfs page buffer. > > Collect each element into a temporary PAGE_SIZE buffer first and then > copy only the remaining space into the caller's page buffer. Should this be using a 4k buffer on all architectures? Initially perhaps just using a different name for the constant until all the associated PAGE_SIZE limits have been removed. -- David > > Cc: stable@vger.kernel.org > Reviewed-by: Petr Pavlu > Signed-off-by: Pengpeng Hou > Signed-off-by: Kees Cook > --- > kernel/params.c | 26 ++++++++++++++++++++------ > 1 file changed, 20 insertions(+), 6 deletions(-) > > diff --git a/kernel/params.c b/kernel/params.c > index 74d620bc2521..752721922a15 100644 > --- a/kernel/params.c > +++ b/kernel/params.c > @@ -475,22 +475,36 @@ static int param_array_set(const char *val, const struct kernel_param *kp) > static int param_array_get(char *buffer, const struct kernel_param *kp) > { > int i, off, ret; > + char *elem_buf; > const struct kparam_array *arr = kp->arr; > struct kernel_param p = *kp; > > + elem_buf = kmalloc(PAGE_SIZE, GFP_KERNEL); > + if (!elem_buf) > + return -ENOMEM; > + > for (i = off = 0; i < (arr->num ? *arr->num : arr->max); i++) { > - /* Replace \n with comma */ > - if (i) > - buffer[off - 1] = ','; > p.arg = arr->elem + arr->elemsize * i; > check_kparam_locked(p.mod); > - ret = arr->ops->get(buffer + off, &p); > + ret = arr->ops->get(elem_buf, &p); > if (ret < 0) > - return ret; > + goto out; > + ret = min(ret, (int)(PAGE_SIZE - 1 - off)); > + if (!ret) > + break; > + /* Replace the previous element's trailing newline with a comma. */ > + if (i) > + buffer[off - 1] = ','; > + memcpy(buffer + off, elem_buf, ret); > off += ret; > + if (off == PAGE_SIZE - 1) > + break; > } > buffer[off] = '\0'; > - return off; > + ret = off; > +out: > + kfree(elem_buf); > + return ret; > } > > static void param_array_free(void *arg)