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Date: Tue, 26 Mar 2019 11:27:34 -0700 From: Matthew Garrett <matthewgarrett@...gle.com> To: jmorris@...ei.org Cc: linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org, dhowells@...hat.com, linux-api@...r.kernel.org, luto@...nel.org, Alan Cox <gnomes@...rguk.ukuu.org.uk>, Matthew Garrett <mjg59@...gle.com> Subject: [PATCH V31 18/25] Lock down module params that specify hardware parameters (eg. ioport) From: David Howells <dhowells@...hat.com> Provided an annotation for module parameters that specify hardware parameters (such as io ports, iomem addresses, irqs, dma channels, fixed dma buffers and other types). Suggested-by: Alan Cox <gnomes@...rguk.ukuu.org.uk> Signed-off-by: David Howells <dhowells@...hat.com> Signed-off-by: Matthew Garrett <mjg59@...gle.com> --- kernel/params.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) diff --git a/kernel/params.c b/kernel/params.c index ce89f757e6da..da1297f7cc26 100644 --- a/kernel/params.c +++ b/kernel/params.c @@ -108,13 +108,19 @@ bool parameq(const char *a, const char *b) return parameqn(a, b, strlen(a)+1); } -static void param_check_unsafe(const struct kernel_param *kp) +static bool param_check_unsafe(const struct kernel_param *kp, + const char *doing) { if (kp->flags & KERNEL_PARAM_FL_UNSAFE) { pr_notice("Setting dangerous option %s - tainting kernel\n", kp->name); add_taint(TAINT_USER, LOCKDEP_STILL_OK); } + + if (kp->flags & KERNEL_PARAM_FL_HWPARAM && + kernel_is_locked_down("Command line-specified device addresses, irqs and dma channels", LOCKDOWN_INTEGRITY)) + return false; + return true; } static int parse_one(char *param, @@ -144,8 +150,10 @@ static int parse_one(char *param, pr_debug("handling %s with %p\n", param, params[i].ops->set); kernel_param_lock(params[i].mod); - param_check_unsafe(¶ms[i]); - err = params[i].ops->set(val, ¶ms[i]); + if (param_check_unsafe(¶ms[i], doing)) + err = params[i].ops->set(val, ¶ms[i]); + else + err = -EPERM; kernel_param_unlock(params[i].mod); return err; } @@ -553,6 +561,12 @@ static ssize_t param_attr_show(struct module_attribute *mattr, return count; } +#ifdef CONFIG_MODULES +#define mod_name(mod) (mod)->name +#else +#define mod_name(mod) "unknown" +#endif + /* sysfs always hands a nul-terminated string in buf. We rely on that. */ static ssize_t param_attr_store(struct module_attribute *mattr, struct module_kobject *mk, @@ -565,8 +579,10 @@ static ssize_t param_attr_store(struct module_attribute *mattr, return -EPERM; kernel_param_lock(mk->mod); - param_check_unsafe(attribute->param); - err = attribute->param->ops->set(buf, attribute->param); + if (param_check_unsafe(attribute->param, mod_name(mk->mod))) + err = attribute->param->ops->set(buf, attribute->param); + else + err = -EPERM; kernel_param_unlock(mk->mod); if (!err) return len; -- 2.21.0.392.gf8f6787159e-goog
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