[18/24] Lock down module params that specify hardware parameters (eg. ioport)

Commit Message

David Howells April 11, 2018, 4:26 p.m. UTC

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 <[e-mail]>
Signed-off-by: David Howells <[e-mail]>
---

 kernel/params.c |   26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)


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Comments

Randy Dunlap April 11, 2018, 5:22 p.m. UTC | #1

On 04/11/2018 09:26 AM, David Howells wrote:
> 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 <[e-mail]>
> Signed-off-by: David Howells <[e-mail]>
> ---
> 
>  kernel/params.c |   26 +++++++++++++++++++++-----
>  1 file changed, 21 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/params.c b/kernel/params.c
> index cc9108c2a1fd..2c08c4aa376b 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_warn("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"))

s/dma/DMA/

Other patches use PCI instead of pci, CIS instead of cis, MMIO instead of mmio,
BPF instead of bpf, MSR instead of msr, etc...


> +		return false;
> +	return true;
>  }
>  
>  static int parse_one(char *param,

Patch

diff --git a/kernel/params.c b/kernel/params.c
index cc9108c2a1fd..2c08c4aa376b 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_warn("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"))
+		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(&params[i]);
-			err = params[i].ops->set(val, &params[i]);
+			if (param_check_unsafe(&params[i], doing))
+				err = params[i].ops->set(val, &params[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;