[added to the 3.18 stable tree] netfilter: x_tables: don't move to non-existent next rule
From: Sasha Levin <hidden>
Date: 2016-07-12 03:05:06
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Florian Westphal <fw@strlen.de> This patch has been added to the 3.18 stable tree. If you have any objections, please let us know. =============== [ Upstream commit f24e230d257af1ad7476c6e81a8dc3127a74204e ] Ben Hawkes says: In the mark_source_chains function (net/ipv4/netfilter/ip_tables.c) it is possible for a user-supplied ipt_entry structure to have a large next_offset field. This field is not bounds checked prior to writing a counter value at the supplied offset. Base chains enforce absolute verdict. User defined chains are supposed to end with an unconditional return, xtables userspace adds them automatically. But if such return is missing we will move to non-existent next rule. Reported-by: Ben Hawkes <redacted> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Sasha Levin <redacted> --- net/ipv4/netfilter/arp_tables.c | 8 +++++--- net/ipv4/netfilter/ip_tables.c | 4 ++++ net/ipv6/netfilter/ip6_tables.c | 4 ++++ 3 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 738e62d..993da4a 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c@@ -435,6 +435,8 @@ static int mark_source_chains(const struct xt_table_info *newinfo, size = e->next_offset; e = (struct arpt_entry *) (entry0 + pos + size); + if (pos + size >= newinfo->size) + return 0; e->counters.pcnt = pos; pos += size; } else {
@@ -457,6 +459,8 @@ static int mark_source_chains(const struct xt_table_info *newinfo, } else { /* ... this is a fallthru */ newpos = pos + e->next_offset; + if (newpos >= newinfo->size) + return 0; } e = (struct arpt_entry *) (entry0 + newpos);
@@ -680,10 +684,8 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0, } } - if (!mark_source_chains(newinfo, repl->valid_hooks, entry0)) { - duprintf("Looping hook\n"); + if (!mark_source_chains(newinfo, repl->valid_hooks, entry0)) return -ELOOP; - } /* Finally, each sanity check must pass */ i = 0;
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 2c8fb72..b75c5bb 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c@@ -516,6 +516,8 @@ mark_source_chains(const struct xt_table_info *newinfo, size = e->next_offset; e = (struct ipt_entry *) (entry0 + pos + size); + if (pos + size >= newinfo->size) + return 0; e->counters.pcnt = pos; pos += size; } else {
@@ -537,6 +539,8 @@ mark_source_chains(const struct xt_table_info *newinfo, } else { /* ... this is a fallthru */ newpos = pos + e->next_offset; + if (newpos >= newinfo->size) + return 0; } e = (struct ipt_entry *) (entry0 + newpos);
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index bc0615b..9367bbd 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c@@ -526,6 +526,8 @@ mark_source_chains(const struct xt_table_info *newinfo, size = e->next_offset; e = (struct ip6t_entry *) (entry0 + pos + size); + if (pos + size >= newinfo->size) + return 0; e->counters.pcnt = pos; pos += size; } else {
@@ -547,6 +549,8 @@ mark_source_chains(const struct xt_table_info *newinfo, } else { /* ... this is a fallthru */ newpos = pos + e->next_offset; + if (newpos >= newinfo->size) + return 0; } e = (struct ip6t_entry *) (entry0 + newpos);
--
2.5.0