netfilter: nft_set_pipapo: fix improper element removal

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2225277
Upstream Status: commit 87b5a5c
CVE: CVE-2023-4004

commit 87b5a5c
Author: Florian Westphal <[email protected]>
Date:   Wed Jul 19 21:08:21 2023 +0200

    netfilter: nft_set_pipapo: fix improper element removal

    end key should be equal to start unless NFT_SET_EXT_KEY_END is present.

    Its possible to add elements that only have a start key
    ("{ 1.0.0.0 . 2.0.0.0 }") without an internval end.

    Insertion treats this via:

    if (nft_set_ext_exists(ext, NFT_SET_EXT_KEY_END))
       end = (const u8 *)nft_set_ext_key_end(ext)->data;
    else
       end = start;

    but removal side always uses nft_set_ext_key_end().
    This is wrong and leads to garbage remaining in the set after removal
    next lookup/insert attempt will give:

    BUG: KASAN: slab-use-after-free in pipapo_get+0x8eb/0xb90
    Read of size 1 at addr ffff888100d50586 by task nft-pipapo_uaf_/1399
    Call Trace:
     kasan_report+0x105/0x140
     pipapo_get+0x8eb/0xb90
     nft_pipapo_insert+0x1dc/0x1710
     nf_tables_newsetelem+0x31f5/0x4e00
     ..

    Fixes: 3c4287f ("nf_tables: Add set type for arbitrary concatenation of ranges")
    Reported-by: lonial con <[email protected]>
    Reviewed-by: Stefano Brivio <[email protected]>
    Signed-off-by: Florian Westphal <[email protected]>

Signed-off-by: Phil Sutter <[email protected]>

Author: SirPhuttel

net/netfilter/nft_set_pipapo.c

@@ -1908,7 +1908,11 @@ static void nft_pipapo_remove(const struct net *net, const struct nft_set *set,
 		int i, start, rules_fx;
 
 		match_start = data;
-		match_end = (const u8 *)nft_set_ext_key_end(&e->ext)->data;
+
+		if (nft_set_ext_exists(&e->ext, NFT_SET_EXT_KEY_END))
+			match_end = (const u8 *)nft_set_ext_key_end(&e->ext)->data;
+		else
+			match_end = data;
 
 		start = first_rule;
 		rules_fx = rules_f0;