[PATCH PKT_SCHED 4/17]: Check TCA_ACT_KIND payload size _before_ copying it

[PATCH PKT_SCHED 4/17]: Check TCA_ACT_KIND payload size _before_ copying it

[Patrick McHardy]

[-- Attachment #1: Type: text/plain, Size: 256 bytes --]

Fix payload size checks like this one:

-                       sprintf(act_name, "%s", (char*)RTA_DATA(kind));
-                       if (RTA_PAYLOAD(kind) >= IFNAMSIZ) {
-                               printk("Action %s bad\n", 
(char*)RTA_DATA(kind))


[-- Attachment #2: 04.diff --]
[-- Type: text/x-patch, Size: 1912 bytes --]

# This is a BitKeeper generated diff -Nru style patch.
#
# ChangeSet
#   2004/12/30 01:45:41+01:00 kaber@coreworks.de 
#   [PKT_SCHED]: Check TCA_ACT_KIND payload size _before_ copying it
#   
#   Signed-off-by: Patrick McHardy <kaber@trash.net>
# 
# net/sched/act_api.c
#   2004/12/30 01:45:35+01:00 kaber@coreworks.de +6 -14
#   [PKT_SCHED]: Check TCA_ACT_KIND payload size _before_ copying it
#   
#   Signed-off-by: Patrick McHardy <kaber@trash.net>
# 
diff -Nru a/net/sched/act_api.c b/net/sched/act_api.c
--- a/net/sched/act_api.c	2004-12-30 04:01:10 +01:00
+++ b/net/sched/act_api.c	2004-12-30 04:01:10 +01:00
@@ -288,11 +288,9 @@
 			goto err_out;
 		kind = tb[TCA_ACT_KIND-1];
 		if (kind != NULL) {
-			sprintf(act_name, "%s", (char*)RTA_DATA(kind));
-			if (RTA_PAYLOAD(kind) >= IFNAMSIZ) {
-				printk("Action %s bad\n", (char*)RTA_DATA(kind));
+			if (RTA_PAYLOAD(kind) >= IFNAMSIZ)
 				goto err_out;
-			}
+			sprintf(act_name, "%s", (char*)RTA_DATA(kind));
 		} else {
 			printk("Action bad kind\n");
 			goto err_out;
@@ -503,12 +501,9 @@
 		goto err_out;
 	kind = tb[TCA_ACT_KIND-1];
 	if (kind != NULL) {
-		sprintf(act_name, "%s", (char*)RTA_DATA(kind));
-		if (RTA_PAYLOAD(kind) >= IFNAMSIZ) {
-			printk("tcf_action_get_1: action %s bad\n",
-			       (char*)RTA_DATA(kind));
+		if (RTA_PAYLOAD(kind) >= IFNAMSIZ)
 			goto err_out;
-		}
+		sprintf(act_name, "%s", (char*)RTA_DATA(kind));
 	} else {
 		printk("tcf_action_get_1: action bad kind\n");
 		goto err_out;
@@ -567,12 +562,9 @@
 	struct tc_action_ops *a_o = NULL;
 
 	if (kind != NULL) {
-		sprintf(act_name, "%s", (char*)RTA_DATA(kind));
-		if (RTA_PAYLOAD(kind) >= IFNAMSIZ) {
-			printk("get_ao: action %s bad\n",
-			       (char*)RTA_DATA(kind));
+		if (RTA_PAYLOAD(kind) >= IFNAMSIZ)
 			return NULL;
-		}
+		sprintf(act_name, "%s", (char*)RTA_DATA(kind));
 	} else {
 		printk("get_ao: action bad kind\n");
 		return NULL;

Re: [PATCH PKT_SCHED 4/17]: Check TCA_ACT_KIND payload size _before_ copying it

[Thomas Graf]

* Patrick McHardy <41D37875.5020103@trash.net> 2004-12-30 04:39
> -			sprintf(act_name, "%s", (char*)RTA_DATA(kind));
> -			if (RTA_PAYLOAD(kind) >= IFNAMSIZ) {
> -				printk("Action %s bad\n", (char*)RTA_DATA(kind));
> +			if (RTA_PAYLOAD(kind) >= IFNAMSIZ)

The check should be RTA_PAYLOAD(kind) > IFNAMSIZ, == is ok
if the terminating NUL is provided.

>  				goto err_out;
> -			}
> +			sprintf(act_name, "%s", (char*)RTA_DATA(kind));
>  		} else {

This will cause horrible crashes if no NUL is provided to terminate
the name.

So I think this should be:

if (RTA_PAYLOAD(kind) > IFNAMSIZ)
	goto err_out;
memset(act_name, ...);
memcpy(act_name, RTA_DATA(kind), RTA_PAYLOAD(kind));
act_name[IFNAMSIZ - 1] = '\0';

The memset is required to ensure 0 termination if kind is not and
shorter than IFNAMSIZ. memcpy instead of str* to avoid using
any form of str(n)len on a possibly not terminated string
and setting IFNAMSIZ - 1 to NUL to ensure proper handling of
a IFNAMSIZ long not terminated string.

I know it's unlikely but this might just save us some troubles later.

Re: [PATCH PKT_SCHED 4/17]: Check TCA_ACT_KIND payload size _before_ copying it

[Patrick McHardy]

Thomas Graf wrote:
> * Patrick McHardy <41D37875.5020103@trash.net> 2004-12-30 04:39
> 
>>-			sprintf(act_name, "%s", (char*)RTA_DATA(kind));
>>-			if (RTA_PAYLOAD(kind) >= IFNAMSIZ) {
>>-				printk("Action %s bad\n", (char*)RTA_DATA(kind));
>>+			if (RTA_PAYLOAD(kind) >= IFNAMSIZ)
> 
> 
> The check should be RTA_PAYLOAD(kind) > IFNAMSIZ, == is ok
> if the terminating NUL is provided.

Thanks.

> 
> 
>> 				goto err_out;
>>-			}
>>+			sprintf(act_name, "%s", (char*)RTA_DATA(kind));
>> 		} else {
> 
> 
> This will cause horrible crashes if no NUL is provided to terminate
> the name.
> 
> So I think this should be:
> 
> if (RTA_PAYLOAD(kind) > IFNAMSIZ)
> 	goto err_out;
> memset(act_name, ...);
> memcpy(act_name, RTA_DATA(kind), RTA_PAYLOAD(kind));
> act_name[IFNAMSIZ - 1] = '\0';
> 
> The memset is required to ensure 0 termination if kind is not and
> shorter than IFNAMSIZ. memcpy instead of str* to avoid using
> any form of str(n)len on a possibly not terminated string
> and setting IFNAMSIZ - 1 to NUL to ensure proper handling of
> a IFNAMSIZ long not terminated string.
> 
> I know it's unlikely but this might just save us some troubles later.

Agreed. I saved this change for later because there are more places
in net/sched that need to be fixed. I guess I'll just add a
rtattr_strncpy function.

Regards
Patrick