From 72239f2795fab9a58633bd0399698ff7581534a3 Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Wed, 1 Apr 2020 17:14:38 +0200 Subject: netfilter: nft_set_rbtree: Drop spurious condition for overlap detection on insertion Case a1. for overlap detection in __nft_rbtree_insert() is not a valid one: start-after-start is not needed to detect any type of interval overlap and it actually results in a false positive if, while descending the tree, this is the only step we hit after starting from the root. This introduced a regression, as reported by Pablo, in Python tests cases ip/ip.t and ip/numgen.t: ip/ip.t: ERROR: line 124: add rule ip test-ip4 input ip hdrlength vmap { 0-4 : drop, 5 : accept, 6 : continue } counter: This rule should not have failed. ip/numgen.t: ERROR: line 7: add rule ip test-ip4 pre dnat to numgen inc mod 10 map { 0-5 : 192.168.10.100, 6-9 : 192.168.20.200}: This rule should not have failed. Drop case a1. and renumber others, so that they are a bit clearer. In order for these diagrams to be readily understandable, a bigger rework is probably needed, such as an ASCII art of the actual rbtree (instead of a flattened version). Shell script test sets/0044interval_overlap_0 should cover all possible cases for false negatives, so I consider that test case still sufficient after this change. v2: Fix comments for cases a3. and b3. Reported-by: Pablo Neira Ayuso Fixes: 7c84d41416d8 ("netfilter: nft_set_rbtree: Detect partial overlaps on insertion") Signed-off-by: Stefano Brivio Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nft_set_rbtree.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) (limited to 'net/netfilter/nft_set_rbtree.c') diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c index 3a5552e14f75..3ffef454d469 100644 --- a/net/netfilter/nft_set_rbtree.c +++ b/net/netfilter/nft_set_rbtree.c @@ -218,27 +218,26 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set, /* Detect overlaps as we descend the tree. Set the flag in these cases: * - * a1. |__ _ _? >|__ _ _ (insert start after existing start) - * a2. _ _ __>| ?_ _ __| (insert end before existing end) - * a3. _ _ ___| ?_ _ _>| (insert end after existing end) - * a4. >|__ _ _ _ _ __| (insert start before existing end) + * a1. _ _ __>| ?_ _ __| (insert end before existing end) + * a2. _ _ ___| ?_ _ _>| (insert end after existing end) + * a3. _ _ ___? >|_ _ __| (insert start before existing end) * * and clear it later on, as we eventually reach the points indicated by * '?' above, in the cases described below. We'll always meet these * later, locally, due to tree ordering, and overlaps for the intervals * that are the closest together are always evaluated last. * - * b1. |__ _ _! >|__ _ _ (insert start after existing end) - * b2. _ _ __>| !_ _ __| (insert end before existing start) - * b3. !_____>| (insert end after existing start) + * b1. _ _ __>| !_ _ __| (insert end before existing start) + * b2. _ _ ___| !_ _ _>| (insert end after existing start) + * b3. _ _ ___! >|_ _ __| (insert start after existing end) * - * Case a4. resolves to b1.: + * Case a3. resolves to b3.: * - if the inserted start element is the leftmost, because the '0' * element in the tree serves as end element * - otherwise, if an existing end is found. Note that end elements are * always inserted after corresponding start elements. * - * For a new, rightmost pair of elements, we'll hit cases b1. and b3., + * For a new, rightmost pair of elements, we'll hit cases b3. and b2., * in that order. * * The flag is also cleared in two special cases: @@ -262,9 +261,9 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set, p = &parent->rb_left; if (nft_rbtree_interval_start(new)) { - overlap = nft_rbtree_interval_start(rbe) && - nft_set_elem_active(&rbe->ext, - genmask); + if (nft_rbtree_interval_end(rbe) && + nft_set_elem_active(&rbe->ext, genmask)) + overlap = false; } else { overlap = nft_rbtree_interval_end(rbe) && nft_set_elem_active(&rbe->ext, -- cgit