From: Florian Westphal Date: Wed, 23 Nov 2016 00:11:03 +0000 (+0100) Subject: netfilter: nat: fix crash when conntrack entry is re-used X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=5173bc679dec881120df109a6a2b39143235382c;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git netfilter: nat: fix crash when conntrack entry is re-used Stas Nichiporovich reports oops in nf_nat_bysource_cmp(), trying to access nf_conn struct at address 0xffffffffffffff50. This is the result of fetching a null rhash list (struct embedded at offset 176; 0 - 176 gets us ...fff50). The problem is that conntrack entries are allocated from a SLAB_DESTROY_BY_RCU cache, i.e. entries can be free'd and reused on another cpu while nf nat bysource hash access the same conntrack entry. Freeing is fine (we hold rcu read lock); zeroing rhlist_head isn't. -> Move the rhlist struct outside of the memset()-inited area. Fixes: 7c9664351980aaa6a ("netfilter: move nat hlist_head to nf_conn") Reported-by: Stas Nichiporovich Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h index dc143ada9762..d9d52c020a70 100644 --- a/include/net/netfilter/nf_conntrack.h +++ b/include/net/netfilter/nf_conntrack.h @@ -100,6 +100,9 @@ struct nf_conn { possible_net_t ct_net; +#if IS_ENABLED(CONFIG_NF_NAT) + struct rhlist_head nat_bysource; +#endif /* all members below initialized via memset */ u8 __nfct_init_offset[0]; @@ -117,9 +120,6 @@ struct nf_conn { /* Extensions */ struct nf_ct_ext *ext; -#if IS_ENABLED(CONFIG_NF_NAT) - struct rhlist_head nat_bysource; -#endif /* Storage reserved for other modules, must be the last member */ union nf_conntrack_proto proto; };