Re: [PATCH V40 19/29] lockdown: Lock down module params that specify hardware parameters (eg. ioport)
From: Jessica Yu <jeyu@kernel.org>
Date: 2019-08-20 16:39:14
Also in:
linux-security-module, lkml
+++ Matthew Garrett [19/08/19 17:17 -0700]:From: David Howells <dhowells@redhat.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 <redacted> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Matthew Garrett <redacted> Reviewed-by: Kees Cook <redacted> Cc: Jessica Yu <jeyu@kernel.org> Signed-off-by: James Morris <jmorris@namei.org>
Acked-by: Jessica Yu <jeyu@kernel.org> Thanks!
quoted hunk ↗ jump to hunk
--- include/linux/security.h | 1 + kernel/params.c | 21 ++++++++++++++++----- security/lockdown/lockdown.c | 1 + 3 files changed, 18 insertions(+), 5 deletions(-)diff --git a/include/linux/security.h b/include/linux/security.h index b4a85badb03a..1a3404f9c060 100644 --- a/include/linux/security.h +++ b/include/linux/security.h@@ -113,6 +113,7 @@ enum lockdown_reason {LOCKDOWN_ACPI_TABLES, LOCKDOWN_PCMCIA_CIS, LOCKDOWN_TIOCSSERIAL, + LOCKDOWN_MODULE_PARAMETERS, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, };diff --git a/kernel/params.c b/kernel/params.c index cf448785d058..8e56f8b12d8f 100644 --- a/kernel/params.c +++ b/kernel/params.c@@ -12,6 +12,7 @@#include <linux/err.h> #include <linux/slab.h> #include <linux/ctype.h> +#include <linux/security.h> #ifdef CONFIG_SYSFS /* Protects all built-in parameters, modules use their own param_lock */@@ -96,13 +97,19 @@ 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) { + if (kp->flags & KERNEL_PARAM_FL_HWPARAM && + security_locked_down(LOCKDOWN_MODULE_PARAMETERS)) + return false; + 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); } + + return true; } static int parse_one(char *param,@@ -132,8 +139,10 @@ 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])) + err = params[i].ops->set(val, ¶ms[i]); + else + err = -EPERM; kernel_param_unlock(params[i].mod); return err; }@@ -553,8 +562,10 @@ 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)) + err = attribute->param->ops->set(buf, attribute->param); + else + err = -EPERM; kernel_param_unlock(mk->mod); if (!err) return len;diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 771c77f9c04a..0fa434294667 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c@@ -28,6 +28,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {[LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables", [LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage", [LOCKDOWN_TIOCSSERIAL] = "reconfiguration of serial port IO", + [LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", }; -- 2.23.0.rc1.153.gdeed80330f-goog