[PATCH net 2/2] netfilter: nf_tables: avoid potential overflows on 32bit arches

[PATCH net 2/2] netfilter: nf_tables: avoid potential overflows on 32bit arches

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

User space could ask for very large hash tables, we need to make sure
our size computations wont overflow.

nf_tables_newset() needs to double check the u64 size
will fit into size_t field.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: 0ed6389c483d ("netfilter: nf_tables: rename set implementations")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_tables_api.c |  7 +++++--
 net/netfilter/nft_set_hash.c  | 10 +++++-----
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 0b7fe0a902ff56c162741e6715ad62d928381ea7..c14213bc714b1a54a4287ae898d3a096b21e00ac 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4184,6 +4184,7 @@ static int nf_tables_newset(struct sk_buff *skb, const struct nfnl_info *info,
 	unsigned char *udata;
 	struct nft_set *set;
 	struct nft_ctx ctx;
+	size_t alloc_size;
 	u64 timeout;
 	char *name;
 	int err, i;
@@ -4329,8 +4330,10 @@ static int nf_tables_newset(struct sk_buff *skb, const struct nfnl_info *info,
 	size = 0;
 	if (ops->privsize != NULL)
 		size = ops->privsize(nla, &desc);
-
-	set = kvzalloc(sizeof(*set) + size + udlen, GFP_KERNEL);
+	alloc_size = sizeof(*set) + size + udlen;
+	if (alloc_size < size)
+		return -ENOMEM;
+	set = kvzalloc(alloc_size, GFP_KERNEL);
 	if (!set)
 		return -ENOMEM;
 
diff --git a/net/netfilter/nft_set_hash.c b/net/netfilter/nft_set_hash.c
index 328f2ce32e4cbd772afe03a10f6d13a7ed6b93d5..7b3d0a78c5696747a2e71b1a58303fa141de6c2b 100644
--- a/net/netfilter/nft_set_hash.c
+++ b/net/netfilter/nft_set_hash.c
@@ -623,7 +623,7 @@ static u64 nft_hash_privsize(const struct nlattr * const nla[],
 			     const struct nft_set_desc *desc)
 {
 	return sizeof(struct nft_hash) +
-	       nft_hash_buckets(desc->size) * sizeof(struct hlist_head);
+	       (u64)nft_hash_buckets(desc->size) * sizeof(struct hlist_head);
 }
 
 static int nft_hash_init(const struct nft_set *set,
@@ -663,8 +663,8 @@ static bool nft_hash_estimate(const struct nft_set_desc *desc, u32 features,
 		return false;
 
 	est->size   = sizeof(struct nft_hash) +
-		      nft_hash_buckets(desc->size) * sizeof(struct hlist_head) +
-		      desc->size * sizeof(struct nft_hash_elem);
+		      (u64)nft_hash_buckets(desc->size) * sizeof(struct hlist_head) +
+		      (u64)desc->size * sizeof(struct nft_hash_elem);
 	est->lookup = NFT_SET_CLASS_O_1;
 	est->space  = NFT_SET_CLASS_O_N;
 
@@ -681,8 +681,8 @@ static bool nft_hash_fast_estimate(const struct nft_set_desc *desc, u32 features
 		return false;
 
 	est->size   = sizeof(struct nft_hash) +
-		      nft_hash_buckets(desc->size) * sizeof(struct hlist_head) +
-		      desc->size * sizeof(struct nft_hash_elem);
+		      (u64)nft_hash_buckets(desc->size) * sizeof(struct hlist_head) +
+		      (u64)desc->size * sizeof(struct nft_hash_elem);
 	est->lookup = NFT_SET_CLASS_O_1;
 	est->space  = NFT_SET_CLASS_O_N;
 
-- 
2.31.1.527.g47e6f16901-goog

Re: [PATCH net 2/2] netfilter: nf_tables: avoid potential overflows on 32bit arches

[Pablo Neira Ayuso]

On Thu, May 06, 2021 at 05:53:50AM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> User space could ask for very large hash tables, we need to make sure
> our size computations wont overflow.
> 
> nf_tables_newset() needs to double check the u64 size
> will fit into size_t field.

Also applied, thannks.