[PATCH 10/30] netfilter: x_tables: enforce unique and ascending entry points
From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: 2018-03-12 17:59:35
Subsystem:
netfilter, networking [general], the rest · Maintainers:
Pablo Neira Ayuso, Florian Westphal, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Florian Westphal <fw@strlen.de> Harmless from kernel point of view, but iptables assumes that this is true when decoding a ruleset. iptables walks the dumped blob from kernel, and, for each entry that creates a new chain it prints out rule/chain information. Base chains (hook entry points) are thus only shown when they appear in the rule blob. One base chain that is referenced multiple times in hook blob is then only printed once. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> --- net/netfilter/x_tables.c | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 5d8ba89a8da8..4e6cbb38e616 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c@@ -529,10 +529,15 @@ static int xt_check_entry_match(const char *match, const char *target, */ int xt_check_table_hooks(const struct xt_table_info *info, unsigned int valid_hooks) { - unsigned int i; + const char *err = "unsorted underflow"; + unsigned int i, max_uflow, max_entry; + bool check_hooks = false; BUILD_BUG_ON(ARRAY_SIZE(info->hook_entry) != ARRAY_SIZE(info->underflow)); + max_entry = 0; + max_uflow = 0; + for (i = 0; i < ARRAY_SIZE(info->hook_entry); i++) { if (!(valid_hooks & (1 << i))) continue;
@@ -541,9 +546,33 @@ int xt_check_table_hooks(const struct xt_table_info *info, unsigned int valid_ho return -EINVAL; if (info->underflow[i] == 0xFFFFFFFF) return -EINVAL; + + if (check_hooks) { + if (max_uflow > info->underflow[i]) + goto error; + + if (max_uflow == info->underflow[i]) { + err = "duplicate underflow"; + goto error; + } + if (max_entry > info->hook_entry[i]) { + err = "unsorted entry"; + goto error; + } + if (max_entry == info->hook_entry[i]) { + err = "duplicate entry"; + goto error; + } + } + max_entry = info->hook_entry[i]; + max_uflow = info->underflow[i]; + check_hooks = true; } return 0; +error: + pr_err_ratelimited("%s at hook %d\n", err, i); + return -EINVAL; } EXPORT_SYMBOL(xt_check_table_hooks);
--
2.11.0