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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id z8sm1756620pjd.0.2021.02.24.20.57.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Feb 2021 20:57:35 -0800 (PST) Date: Wed, 24 Feb 2021 20:57:34 -0800 From: Kees Cook To: Nathan Chancellor , "Michael S. Tsirkin" Subject: Re: [PATCH] qemu_fw_cfg: Make fw_cfg_rev_attr a proper kobj_attribute Message-ID: <202102242050.128D0CD@keescook> References: <20210211194258.4137998-1-nathan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210211194258.4137998-1-nathan@kernel.org> Received-SPF: pass client-ip=2607:f8b0:4864:20::1033; envelope-from=keescook@chromium.org; helo=mail-pj1-x1033.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Gabriel Somlo , Nick Desaulniers , qemu-devel@nongnu.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Sami Tolvanen Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Feb 11, 2021 at 12:42:58PM -0700, Nathan Chancellor wrote: > fw_cfg_showrev() is called by an indirect call in kobj_attr_show(), > which violates clang's CFI checking because fw_cfg_showrev()'s second > parameter is 'struct attribute', whereas the ->show() member of 'struct > kobj_structure' expects the second parameter to be of type 'struct > kobj_attribute'. > > $ cat /sys/firmware/qemu_fw_cfg/rev > 3 > > $ dmesg | grep "CFI failure" > [ 26.016832] CFI failure (target: fw_cfg_showrev+0x0/0x8): > > Fix this by converting fw_cfg_rev_attr to 'struct kobj_attribute' where > this would have been caught automatically by the incompatible pointer > types compiler warning. Update fw_cfg_showrev() accordingly. > > Fixes: 75f3e8e47f38 ("firmware: introduce sysfs driver for QEMU's fw_cfg device") > Link: https://github.com/ClangBuiltLinux/linux/issues/1299 > Signed-off-by: Nathan Chancellor Ah, nice, yes. Reviewed-by: Kees Cook Michael, are you able to take this? I can snag it if needed. -Kees > --- > drivers/firmware/qemu_fw_cfg.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c > index 0078260fbabe..172c751a4f6c 100644 > --- a/drivers/firmware/qemu_fw_cfg.c > +++ b/drivers/firmware/qemu_fw_cfg.c > @@ -299,15 +299,13 @@ static int fw_cfg_do_platform_probe(struct platform_device *pdev) > return 0; > } > > -static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char *buf) > +static ssize_t fw_cfg_showrev(struct kobject *k, struct kobj_attribute *a, > + char *buf) > { > return sprintf(buf, "%u\n", fw_cfg_rev); > } > > -static const struct { > - struct attribute attr; > - ssize_t (*show)(struct kobject *k, struct attribute *a, char *buf); > -} fw_cfg_rev_attr = { > +static const struct kobj_attribute fw_cfg_rev_attr = { > .attr = { .name = "rev", .mode = S_IRUSR }, > .show = fw_cfg_showrev, > }; > > base-commit: 92bf22614b21a2706f4993b278017e437f7785b3 > -- > 2.30.1 > -- Kees Cook