From 4c70c227fdbb4ec302286bb7ade2ec4051b4d508 Mon Sep 17 00:00:00 2001 From: Vishwanath Pai Date: Wed, 16 Mar 2016 09:03:30 +0100 Subject: netfilter: ipset: fix race condition in ipset save, swap and delete This fix adds a new reference counter (ref_netlink) for the struct ip_set. The other reference counter (ref) can be swapped out by ip_set_swap and we need a separate counter to keep track of references for netlink events like dump. Using the same ref counter for dump causes a race condition which can be demonstrated by the following script: ipset create hash_ip1 hash:ip family inet hashsize 1024 maxelem 500000 \ counters ipset create hash_ip2 hash:ip family inet hashsize 300000 maxelem 500000 \ counters ipset create hash_ip3 hash:ip family inet hashsize 1024 maxelem 500000 \ counters ipset save & ipset swap hash_ip3 hash_ip2 ipset destroy hash_ip3 /* will crash the machine */ Swap will exchange the values of ref so destroy will see ref = 0 instead of ref = 1. With this fix in place swap will not succeed because ipset save still has ref_netlink on the set (ip_set_swap doesn't swap ref_netlink). Both delete and swap will error out if ref_netlink != 0 on the set. Note: The changes to *_head functions is because previously we would increment ref whenever we called these functions, we don't do that anymore. Reviewed-by: Joshua Hunt Signed-off-by: Vishwanath Pai Signed-off-by: Jozsef Kadlecsik --- kernel/include/linux/netfilter/ipset/ip_set.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'kernel/include/linux/netfilter/ipset/ip_set.h') diff --git a/kernel/include/linux/netfilter/ipset/ip_set.h b/kernel/include/linux/netfilter/ipset/ip_set.h index eaf5057..3e44e66 100644 --- a/kernel/include/linux/netfilter/ipset/ip_set.h +++ b/kernel/include/linux/netfilter/ipset/ip_set.h @@ -235,6 +235,10 @@ struct ip_set { spinlock_t lock; /* References to the set */ u32 ref; + /* References to the set for netlink events like dump, + * ref can be swapped out by ip_set_swap + */ + u32 ref_netlink; /* The core set type */ struct ip_set_type *type; /* The type variant doing the real job */ -- cgit v1.2.3