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netfilter: nft_set_rbtree: fix null deref on element insertion

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There is no guarantee that rb_prev() will not return NULL in nft_rbtree_gc_elem():

general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
 nft_add_set_elem+0x14b0/0x2990
  nf_tables_newsetelem+0x528/0xb30

Furthermore, there is a possible use-after-free while iterating,
'node' can be free'd so we need to cache the next value to use.

Fixes: c9e6978e27 ("netfilter: nft_set_rbtree: Switch to node list walk for overlap detection")
Signed-off-by: Florian Westphal <fw@strlen.de>
This commit is contained in:
Florian Westphal 2023-05-11 22:39:30 +02:00
parent e3c361b8ac
commit 61ae320a29
1 changed files with 13 additions and 7 deletions
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20
net/netfilter/nft_set_rbtree.c
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@ -221,7 +221,7 @@ static int nft_rbtree_gc_elem(const struct nft_set *__set,
{
struct nft_set *set = (struct nft_set *)__set;
struct rb_node *prev = rb_prev(&rbe->node);
struct nft_rbtree_elem *rbe_prev;
struct nft_rbtree_elem *rbe_prev = NULL;
struct nft_set_gc_batch *gcb;
gcb = nft_set_gc_batch_check(set, NULL, GFP_ATOMIC);
@ -229,17 +229,21 @@ static int nft_rbtree_gc_elem(const struct nft_set *__set,
return -ENOMEM;
/* search for expired end interval coming before this element. */
do {
while (prev) {
rbe_prev = rb_entry(prev, struct nft_rbtree_elem, node);
if (nft_rbtree_interval_end(rbe_prev))
break;
prev = rb_prev(prev);
} while (prev != NULL);
}
if (rbe_prev) {
rb_erase(&rbe_prev->node, &priv->root);
atomic_dec(&set->nelems);
}
rb_erase(&rbe_prev->node, &priv->root);
rb_erase(&rbe->node, &priv->root);
atomic_sub(2, &set->nelems);
atomic_dec(&set->nelems);
nft_set_gc_batch_add(gcb, rbe);
nft_set_gc_batch_complete(gcb);
@ -268,7 +272,7 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set,
struct nft_set_ext **ext)
{
struct nft_rbtree_elem *rbe, *rbe_le = NULL, *rbe_ge = NULL;
struct rb_node *node, *parent, **p, *first = NULL;
struct rb_node *node, *next, *parent, **p, *first = NULL;
struct nft_rbtree *priv = nft_set_priv(set);
u8 genmask = nft_genmask_next(net);
int d, err;
@ -307,7 +311,9 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set,
* Values stored in the tree are in reversed order, starting from
* highest to lowest value.
*/
for (node = first; node != NULL; node = rb_next(node)) {
for (node = first; node != NULL; node = next) {
next = rb_next(node);
rbe = rb_entry(node, struct nft_rbtree_elem, node);
if (!nft_set_elem_active(&rbe->ext, genmask))