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netfilter: nft_set_rbtree: Detect partial overlaps on insertion

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...and return -ENOTEMPTY to the front-end in this case, instead of
proceeding. Currently, nft takes care of checking for these cases
and not sending them to the kernel, but if we drop the set_overlap()
call in nft we can end up in situations like:

 # nft add table t
 # nft add set t s '{ type inet_service ; flags interval ; }'
 # nft add element t s '{ 1 - 5 }'
 # nft add element t s '{ 6 - 10 }'
 # nft add element t s '{ 4 - 7 }'
 # nft list set t s
 table ip t {
 	set s {
 		type inet_service
 		flags interval
 		elements = { 1-3, 4-5, 6-7 }
 	}
 }

This change has the primary purpose of making the behaviour
consistent with nft_set_pipapo, but is also functional to avoid
inconsistent behaviour if userspace sends overlapping elements for
any reason.

v2: When we meet the same key data in the tree, as start element while
    inserting an end element, or as end element while inserting a start
    element, actually check that the existing element is active, before
    resetting the overlap flag (Pablo Neira Ayuso)

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Stefano Brivio 2020-03-22 03:22:01 +01:00 committed by Pablo Neira Ayuso
parent 6f7c9caf01
commit 7c84d41416
1 changed files with 67 additions and 3 deletions
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70
net/netfilter/nft_set_rbtree.c
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@ -213,8 +213,43 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set,
u8 genmask = nft_genmask_next(net);
struct nft_rbtree_elem *rbe;
struct rb_node *parent, **p;
bool overlap = false;
int d;
/* 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)
*
* 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)
*
* Case a4. resolves to b1.:
* - 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.,
* in that order.
*
* The flag is also cleared in two special cases:
*
* b4. |__ _ _!|<_ _ _ (insert start right before existing end)
* b5. |__ _ >|!__ _ _ (insert end right after existing start)
*
* which always happen as last step and imply that no further
* overlapping is possible.
*/
parent = NULL;
p = &priv->root.rb_node;
while (*p != NULL) {
@ -223,17 +258,42 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set,
d = memcmp(nft_set_ext_key(&rbe->ext),
nft_set_ext_key(&new->ext),
set->klen);
if (d < 0)
if (d < 0) {
p = &parent->rb_left;
else if (d > 0)
if (nft_rbtree_interval_start(new)) {
overlap = nft_rbtree_interval_start(rbe) &&
nft_set_elem_active(&rbe->ext,
genmask);
} else {
overlap = nft_rbtree_interval_end(rbe) &&
nft_set_elem_active(&rbe->ext,
genmask);
}
} else if (d > 0) {
p = &parent->rb_right;
else {
if (nft_rbtree_interval_end(new)) {
overlap = nft_rbtree_interval_end(rbe) &&
nft_set_elem_active(&rbe->ext,
genmask);
} else if (nft_rbtree_interval_end(rbe) &&
nft_set_elem_active(&rbe->ext, genmask)) {
overlap = true;
}
} else {
if (nft_rbtree_interval_end(rbe) &&
nft_rbtree_interval_start(new)) {
p = &parent->rb_left;
if (nft_set_elem_active(&rbe->ext, genmask))
overlap = false;
} else if (nft_rbtree_interval_start(rbe) &&
nft_rbtree_interval_end(new)) {
p = &parent->rb_right;
if (nft_set_elem_active(&rbe->ext, genmask))
overlap = false;
} else if (nft_set_elem_active(&rbe->ext, genmask)) {
*ext = &rbe->ext;
return -EEXIST;
@ -242,6 +302,10 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set,
}
}
}
if (overlap)
return -ENOTEMPTY;
rb_link_node_rcu(&new->node, parent, p);
rb_insert_color(&new->node, &priv->root);
return 0;