Re: [PATCH nf-next] netfilter: xtables: avoid BUG_ON

[Pablo Neira Ayuso]

On Tue, Sep 04, 2018 at 04:01:57PM +0200, Florian Westphal wrote:
> I see no reason for them, label or timer cannot be NULL, and if they
> were, we'll crash with null deref anyway.
> 
> For skb_header_pointer failure, just set hotdrop to true and toss
> such packet.

Applied, thanks.

[PATCH nf-next] netfilter: xtables: avoid BUG_ON

[Florian Westphal]

I see no reason for them, label or timer cannot be NULL, and if they
were, we'll crash with null deref anyway.

For skb_header_pointer failure, just set hotdrop to true and toss
such packet.

Signed-off-by: Florian Westphal 
---
 net/ipv6/netfilter/ip6t_ipv6header.c |  5 -
 net/ipv6/netfilter/ip6t_rt.c | 10 --
 net/netfilter/xt_IDLETIMER.c |  4 
 net/netfilter/xt_SECMARK.c   |  2 --
 4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/netfilter/ip6t_ipv6header.c 
b/net/ipv6/netfilter/ip6t_ipv6header.c
index 8b147440fbdc..af737b47b9b5 100644
--- a/net/ipv6/netfilter/ip6t_ipv6header.c
+++ b/net/ipv6/netfilter/ip6t_ipv6header.c
@@ -65,7 +65,10 @@ ipv6header_mt6(const struct sk_buff *skb, struct 
xt_action_param *par)
}
 
hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
-   BUG_ON(hp == NULL);
+   if (!hp) {
+   par->hotdrop = true;
+   return false;
+   }
 
/* Calculate the header length */
if (nexthdr == NEXTHDR_FRAGMENT)
diff --git a/net/ipv6/netfilter/ip6t_rt.c b/net/ipv6/netfilter/ip6t_rt.c
index 2c99b94eeca3..21bf6bf04323 100644
--- a/net/ipv6/netfilter/ip6t_rt.c
+++ b/net/ipv6/netfilter/ip6t_rt.c
@@ -137,7 +137,10 @@ static bool rt_mt6(const struct sk_buff *skb, struct 
xt_action_param *par)
sizeof(_addr),
&_addr);
 
-   BUG_ON(ap == NULL);
+   if (ap == NULL) {
+   par->hotdrop = true;
+   return false;
+   }
 
if (ipv6_addr_equal(ap, >addrs[i])) {
pr_debug("i=%d temp=%d;\n", i, temp);
@@ -166,7 +169,10 @@ static bool rt_mt6(const struct sk_buff *skb, struct 
xt_action_param *par)
+ temp * sizeof(_addr),
sizeof(_addr),
&_addr);
-   BUG_ON(ap == NULL);
+   if (ap == NULL) {
+   par->hotdrop = true;
+   return false;
+   }
 
if (!ipv6_addr_equal(ap, >addrs[temp]))
break;
diff --git a/net/netfilter/xt_IDLETIMER.c b/net/netfilter/xt_IDLETIMER.c
index 5ee859193783..c6acfc2d9c84 100644
--- a/net/netfilter/xt_IDLETIMER.c
+++ b/net/netfilter/xt_IDLETIMER.c
@@ -68,8 +68,6 @@ struct idletimer_tg *__idletimer_tg_find_by_label(const char 
*label)
 {
struct idletimer_tg *entry;
 
-   BUG_ON(!label);
-
list_for_each_entry(entry, _tg_list, entry) {
if (!strcmp(label, entry->attr.attr.name))
return entry;
@@ -172,8 +170,6 @@ static unsigned int idletimer_tg_target(struct sk_buff *skb,
pr_debug("resetting timer %s, timeout period %u\n",
 info->label, info->timeout);
 
-   BUG_ON(!info->timer);
-
mod_timer(>timer->timer,
  msecs_to_jiffies(info->timeout * 1000) + jiffies);
 
diff --git a/net/netfilter/xt_SECMARK.c b/net/netfilter/xt_SECMARK.c
index 4ad5fe27e08b..f16202d26c20 100644
--- a/net/netfilter/xt_SECMARK.c
+++ b/net/netfilter/xt_SECMARK.c
@@ -35,8 +35,6 @@ secmark_tg(struct sk_buff *skb, const struct xt_action_param 
*par)
u32 secmark = 0;
const struct xt_secmark_target_info *info = par->targinfo;
 
-   BUG_ON(info->mode != mode);
-
switch (mode) {
case SECMARK_MODE_SEL:
secmark = info->secid;
-- 
2.16.4