[PATCH net 0/2] Netfilter fixes for net

[PATCH net 0/2] Netfilter fixes for net

[Pablo Neira Ayuso]

Hi,

The following patchset contains Netfilter fixes for net:

1) Fix UAF when creating non-stateful expression in set.

2) Set limit cost when cloning expression accordingly, from Phil Sutter.

Please, pull these changes from:

  git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git

Thanks.

----------------------------------------------------------------

The following changes since commit 6c465408a7709cf180cde7569e141191b67a175c:

  dt-bindings: net: adin: Fix adi,phy-output-clock description syntax (2022-05-25 22:03:45 -0700)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git HEAD

for you to fetch changes up to 558254b0b602b8605d7246a10cfeb584b1fcabfc:

  netfilter: nft_limit: Clone packet limits' cost value (2022-05-26 22:50:34 +0200)

----------------------------------------------------------------
Pablo Neira Ayuso (1):
      netfilter: nf_tables: disallow non-stateful expression in sets earlier

Phil Sutter (1):
      netfilter: nft_limit: Clone packet limits' cost value

 net/netfilter/nf_tables_api.c | 19 ++++++++++---------
 net/netfilter/nft_limit.c     |  2 ++
 2 files changed, 12 insertions(+), 9 deletions(-)

[PATCH net 1/2] netfilter: nf_tables: disallow non-stateful expression in sets earlier

[Pablo Neira Ayuso]

Since 3e135cd499bf ("netfilter: nft_dynset: dynamic stateful expression
instantiation"), it is possible to attach stateful expressions to set
elements.

cd5125d8f518 ("netfilter: nf_tables: split set destruction in deactivate
and destroy phase") introduces conditional destruction on the object to
accomodate transaction semantics.

nft_expr_init() calls expr->ops->init() first, then check for
NFT_STATEFUL_EXPR, this stills allows to initialize a non-stateful
lookup expressions which points to a set, which might lead to UAF since
the set is not properly detached from the set->binding for this case.
Anyway, this combination is non-sense from nf_tables perspective.

This patch fixes this problem by checking for NFT_STATEFUL_EXPR before
expr->ops->init() is called.

The reporter provides a KASAN splat and a poc reproducer (similar to
those autogenerated by syzbot to report use-after-free errors). It is
unknown to me if they are using syzbot or if they use similar automated
tool to locate the bug that they are reporting.

For the record, this is the KASAN splat.

[   85.431824] ==================================================================
[   85.432901] BUG: KASAN: use-after-free in nf_tables_bind_set+0x81b/0xa20
[   85.433825] Write of size 8 at addr ffff8880286f0e98 by task poc/776
[   85.434756]
[   85.434999] CPU: 1 PID: 776 Comm: poc Tainted: G        W         5.18.0+ #2
[   85.436023] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014

Fixes: 0b2d8a7b638b ("netfilter: nf_tables: add helper functions for expression handling")
Reported-and-tested-by: Aaron Adams <edg-e@nccgroup.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_tables_api.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 12fc9cda4a2c..f296dfe86b62 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -2873,27 +2873,31 @@ static struct nft_expr *nft_expr_init(const struct nft_ctx *ctx,
 
 	err = nf_tables_expr_parse(ctx, nla, &expr_info);
 	if (err < 0)
-		goto err1;
+		goto err_expr_parse;
+
+	err = -EOPNOTSUPP;
+	if (!(expr_info.ops->type->flags & NFT_EXPR_STATEFUL))
+		goto err_expr_stateful;
 
 	err = -ENOMEM;
 	expr = kzalloc(expr_info.ops->size, GFP_KERNEL_ACCOUNT);
 	if (expr == NULL)
-		goto err2;
+		goto err_expr_stateful;
 
 	err = nf_tables_newexpr(ctx, &expr_info, expr);
 	if (err < 0)
-		goto err3;
+		goto err_expr_new;
 
 	return expr;
-err3:
+err_expr_new:
 	kfree(expr);
-err2:
+err_expr_stateful:
 	owner = expr_info.ops->type->owner;
 	if (expr_info.ops->type->release_ops)
 		expr_info.ops->type->release_ops(expr_info.ops);
 
 	module_put(owner);
-err1:
+err_expr_parse:
 	return ERR_PTR(err);
 }
 
@@ -5413,9 +5417,6 @@ struct nft_expr *nft_set_elem_expr_alloc(const struct nft_ctx *ctx,
 		return expr;
 
 	err = -EOPNOTSUPP;
-	if (!(expr->ops->type->flags & NFT_EXPR_STATEFUL))
-		goto err_set_elem_expr;
-
 	if (expr->ops->type->flags & NFT_EXPR_GC) {
 		if (set->flags & NFT_SET_TIMEOUT)
 			goto err_set_elem_expr;
-- 
2.30.2

[PATCH net 2/2] netfilter: nft_limit: Clone packet limits' cost value

[Pablo Neira Ayuso]

From: Phil Sutter <phil@nwl.cc>

When cloning a packet-based limit expression, copy the cost value as
well. Otherwise the new limit is not functional anymore.

Fixes: 3b9e2ea6c11bf ("netfilter: nft_limit: move stateful fields out of expression data")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nft_limit.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/netfilter/nft_limit.c b/net/netfilter/nft_limit.c
index 04ea8b9bf202..981addb2d051 100644
--- a/net/netfilter/nft_limit.c
+++ b/net/netfilter/nft_limit.c
@@ -213,6 +213,8 @@ static int nft_limit_pkts_clone(struct nft_expr *dst, const struct nft_expr *src
 	struct nft_limit_priv_pkts *priv_dst = nft_expr_priv(dst);
 	struct nft_limit_priv_pkts *priv_src = nft_expr_priv(src);
 
+	priv_dst->cost = priv_src->cost;
+
 	return nft_limit_clone(&priv_dst->limit, &priv_src->limit);
 }
 
-- 
2.30.2

Re: [PATCH net 1/2] netfilter: nf_tables: disallow non-stateful expression in sets earlier

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf.git (master)
by Pablo Neira Ayuso <pablo@netfilter.org>:

On Thu, 26 May 2022 22:54:10 +0200 you wrote:
> Since 3e135cd499bf ("netfilter: nft_dynset: dynamic stateful expression
> instantiation"), it is possible to attach stateful expressions to set
> elements.
> 
> cd5125d8f518 ("netfilter: nf_tables: split set destruction in deactivate
> and destroy phase") introduces conditional destruction on the object to
> accomodate transaction semantics.
> 
> [...]

Here is the summary with links:
  - [net,1/2] netfilter: nf_tables: disallow non-stateful expression in sets earlier
    https://git.kernel.org/bpf/bpf/c/520778042ccc
  - [net,2/2] netfilter: nft_limit: Clone packet limits' cost value
    https://git.kernel.org/bpf/bpf/c/558254b0b602

You are awesome, thank you!
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