From 7ed2abddd20cf8f6bd27f65bd218f26fa5bf7f44 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 1 Apr 2016 14:17:27 +0200 Subject: [PATCH] netfilter: x_tables: check standard target size too We have targets and standard targets -- the latter carries a verdict. The ip/ip6tables validation functions will access t->verdict for the standard targets to fetch the jump offset or verdict for chainloop detection, but this happens before the targets get checked/validated. Thus we also need to check for verdict presence here, else t->verdict can point right after a blob. Spotted with UBSAN while testing malformed blobs. Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/x_tables.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index fa206ceb269f..1cb7a271c024 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c @@ -540,6 +540,13 @@ int xt_compat_match_to_user(const struct xt_entry_match *m, } EXPORT_SYMBOL_GPL(xt_compat_match_to_user); +/* non-compat version may have padding after verdict */ +struct compat_xt_standard_target { + struct compat_xt_entry_target t; + compat_uint_t verdict; +}; + +/* see xt_check_entry_offsets */ int xt_compat_check_entry_offsets(const void *base, unsigned int target_offset, unsigned int next_offset) @@ -557,6 +564,10 @@ int xt_compat_check_entry_offsets(const void *base, if (target_offset + t->u.target_size > next_offset) return -EINVAL; + if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 && + target_offset + sizeof(struct compat_xt_standard_target) != next_offset) + return -EINVAL; + return 0; } EXPORT_SYMBOL(xt_compat_check_entry_offsets); @@ -596,6 +607,10 @@ int xt_check_entry_offsets(const void *base, if (target_offset + t->u.target_size > next_offset) return -EINVAL; + if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 && + target_offset + sizeof(struct xt_standard_target) != next_offset) + return -EINVAL; + return 0; } EXPORT_SYMBOL(xt_check_entry_offsets); -- 2.20.1