[PATCH net 0/3] Netfilter fixes for net

[PATCH net 0/3] Netfilter fixes for net

[Pablo Neira Ayuso]

Hi Jakub, David,

The following patchset contains Netfilter fixes for net:

1) Missing sanitization of rateest userspace string, bug has been
   triggered by syzbot, patch from Florian Westphal.

2) Report EOPNOTSUPP on missing set features in nft_dynset, otherwise
   error reporting to userspace via EINVAL is misleading since this is
   reserved for malformed netlink requests.

3) New binaries with old kernels might silently accept several set
   element expressions. New binaries set on the NFT_SET_EXPR and
   NFT_DYNSET_F_EXPR flags to request for several expressions per
   element, hence old kernels which do not support for this bail out
   with EOPNOTSUPP.

Please, pull these changes from:

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

Thanks!

P.S: Best wishes for 2021.

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

The following changes since commit 1f45dc22066797479072978feeada0852502e180:

  ibmvnic: continue fatal error reset after passive init (2020-12-23 12:56:10 -0800)

are available in the Git repository at:

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

for you to fetch changes up to b4e70d8dd9ea6bd5d5fb3122586f652326ca09cd:

  netfilter: nftables: add set expression flags (2020-12-28 10:50:26 +0100)

----------------------------------------------------------------
Florian Westphal (1):
      netfilter: xt_RATEEST: reject non-null terminated string from userspace

Pablo Neira Ayuso (2):
      netfilter: nft_dynset: report EOPNOTSUPP on missing set feature
      netfilter: nftables: add set expression flags

 include/uapi/linux/netfilter/nf_tables.h |  3 +++
 net/netfilter/nf_tables_api.c            |  6 +++++-
 net/netfilter/nft_dynset.c               | 15 ++++++++++-----
 net/netfilter/xt_RATEEST.c               |  3 +++
 4 files changed, 21 insertions(+), 6 deletions(-)

[PATCH net 1/3] netfilter: xt_RATEEST: reject non-null terminated string from userspace

[Pablo Neira Ayuso]

From: Florian Westphal <fw@strlen.de>

syzbot reports:
detected buffer overflow in strlen
[..]
Call Trace:
 strlen include/linux/string.h:325 [inline]
 strlcpy include/linux/string.h:348 [inline]
 xt_rateest_tg_checkentry+0x2a5/0x6b0 net/netfilter/xt_RATEEST.c:143

strlcpy assumes src is a c-string. Check info->name before its used.

Reported-by: syzbot+e86f7c428c8c50db65b4@syzkaller.appspotmail.com
Fixes: 5859034d7eb8793 ("[NETFILTER]: x_tables: add RATEEST target")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/xt_RATEEST.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/netfilter/xt_RATEEST.c b/net/netfilter/xt_RATEEST.c
index 37253d399c6b..0d5c422f8745 100644
--- a/net/netfilter/xt_RATEEST.c
+++ b/net/netfilter/xt_RATEEST.c
@@ -115,6 +115,9 @@ static int xt_rateest_tg_checkentry(const struct xt_tgchk_param *par)
 	} cfg;
 	int ret;
 
+	if (strnlen(info->name, sizeof(est->name)) >= sizeof(est->name))
+		return -ENAMETOOLONG;
+
 	net_get_random_once(&jhash_rnd, sizeof(jhash_rnd));
 
 	mutex_lock(&xn->hash_lock);
-- 
2.20.1

[PATCH net 2/3] netfilter: nft_dynset: report EOPNOTSUPP on missing set feature

[Pablo Neira Ayuso]

If userspace requests a feature which is not available the original set
definition, then bail out with EOPNOTSUPP. If userspace sends
unsupported dynset flags (new feature not supported by this kernel),
then report EOPNOTSUPP to userspace. EINVAL should be only used to
report malformed netlink messages from userspace.

Fixes: 22fe54d5fefc ("netfilter: nf_tables: add support for dynamic set updates")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nft_dynset.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nft_dynset.c b/net/netfilter/nft_dynset.c
index 983a1d5ca3ab..f35df221a633 100644
--- a/net/netfilter/nft_dynset.c
+++ b/net/netfilter/nft_dynset.c
@@ -177,7 +177,7 @@ static int nft_dynset_init(const struct nft_ctx *ctx,
 		u32 flags = ntohl(nla_get_be32(tb[NFTA_DYNSET_FLAGS]));
 
 		if (flags & ~NFT_DYNSET_F_INV)
-			return -EINVAL;
+			return -EOPNOTSUPP;
 		if (flags & NFT_DYNSET_F_INV)
 			priv->invert = true;
 	}
@@ -210,7 +210,7 @@ static int nft_dynset_init(const struct nft_ctx *ctx,
 	timeout = 0;
 	if (tb[NFTA_DYNSET_TIMEOUT] != NULL) {
 		if (!(set->flags & NFT_SET_TIMEOUT))
-			return -EINVAL;
+			return -EOPNOTSUPP;
 
 		err = nf_msecs_to_jiffies64(tb[NFTA_DYNSET_TIMEOUT], &timeout);
 		if (err)
@@ -224,7 +224,7 @@ static int nft_dynset_init(const struct nft_ctx *ctx,
 
 	if (tb[NFTA_DYNSET_SREG_DATA] != NULL) {
 		if (!(set->flags & NFT_SET_MAP))
-			return -EINVAL;
+			return -EOPNOTSUPP;
 		if (set->dtype == NFT_DATA_VERDICT)
 			return -EOPNOTSUPP;
 
-- 
2.20.1

[PATCH net 3/3] netfilter: nftables: add set expression flags

[Pablo Neira Ayuso]

The set flag NFT_SET_EXPR provides a hint to the kernel that userspace
supports for multiple expressions per set element. In the same
direction, NFT_DYNSET_F_EXPR specifies that dynset expression defines
multiple expressions per set element.

This allows new userspace software with old kernels to bail out with
EOPNOTSUPP. This update is similar to ef516e8625dd ("netfilter:
nf_tables: reintroduce the NFT_SET_CONCAT flag"). The NFT_SET_EXPR flag
needs to be set on when the NFTA_SET_EXPRESSIONS attribute is specified.
The NFT_SET_EXPR flag is not set on with NFTA_SET_EXPR to retain
backward compatibility in old userspace binaries.

Fixes: 48b0ae046ee9 ("netfilter: nftables: netlink support for several set element expressions")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/uapi/linux/netfilter/nf_tables.h | 3 +++
 net/netfilter/nf_tables_api.c            | 6 +++++-
 net/netfilter/nft_dynset.c               | 9 +++++++--
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 28b6ee53305f..b1633e7ba529 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -293,6 +293,7 @@ enum nft_rule_compat_attributes {
  * @NFT_SET_EVAL: set can be updated from the evaluation path
  * @NFT_SET_OBJECT: set contains stateful objects
  * @NFT_SET_CONCAT: set contains a concatenation
+ * @NFT_SET_EXPR: set contains expressions
  */
 enum nft_set_flags {
 	NFT_SET_ANONYMOUS		= 0x1,
@@ -303,6 +304,7 @@ enum nft_set_flags {
 	NFT_SET_EVAL			= 0x20,
 	NFT_SET_OBJECT			= 0x40,
 	NFT_SET_CONCAT			= 0x80,
+	NFT_SET_EXPR			= 0x100,
 };
 
 /**
@@ -706,6 +708,7 @@ enum nft_dynset_ops {
 
 enum nft_dynset_flags {
 	NFT_DYNSET_F_INV	= (1 << 0),
+	NFT_DYNSET_F_EXPR	= (1 << 1),
 };
 
 /**
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 4186b1e52d58..15c467f1a9dd 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -4162,7 +4162,7 @@ static int nf_tables_newset(struct net *net, struct sock *nlsk,
 		if (flags & ~(NFT_SET_ANONYMOUS | NFT_SET_CONSTANT |
 			      NFT_SET_INTERVAL | NFT_SET_TIMEOUT |
 			      NFT_SET_MAP | NFT_SET_EVAL |
-			      NFT_SET_OBJECT | NFT_SET_CONCAT))
+			      NFT_SET_OBJECT | NFT_SET_CONCAT | NFT_SET_EXPR))
 			return -EOPNOTSUPP;
 		/* Only one of these operations is supported */
 		if ((flags & (NFT_SET_MAP | NFT_SET_OBJECT)) ==
@@ -4304,6 +4304,10 @@ static int nf_tables_newset(struct net *net, struct sock *nlsk,
 		struct nlattr *tmp;
 		int left;
 
+		if (!(flags & NFT_SET_EXPR)) {
+			err = -EINVAL;
+			goto err_set_alloc_name;
+		}
 		i = 0;
 		nla_for_each_nested(tmp, nla[NFTA_SET_EXPRESSIONS], left) {
 			if (i == NFT_SET_EXPR_MAX) {
diff --git a/net/netfilter/nft_dynset.c b/net/netfilter/nft_dynset.c
index f35df221a633..0b053f75cd60 100644
--- a/net/netfilter/nft_dynset.c
+++ b/net/netfilter/nft_dynset.c
@@ -19,6 +19,7 @@ struct nft_dynset {
 	enum nft_registers		sreg_key:8;
 	enum nft_registers		sreg_data:8;
 	bool				invert;
+	bool				expr;
 	u8				num_exprs;
 	u64				timeout;
 	struct nft_expr			*expr_array[NFT_SET_EXPR_MAX];
@@ -175,11 +176,12 @@ static int nft_dynset_init(const struct nft_ctx *ctx,
 
 	if (tb[NFTA_DYNSET_FLAGS]) {
 		u32 flags = ntohl(nla_get_be32(tb[NFTA_DYNSET_FLAGS]));
-
-		if (flags & ~NFT_DYNSET_F_INV)
+		if (flags & ~(NFT_DYNSET_F_INV | NFT_DYNSET_F_EXPR))
 			return -EOPNOTSUPP;
 		if (flags & NFT_DYNSET_F_INV)
 			priv->invert = true;
+		if (flags & NFT_DYNSET_F_EXPR)
+			priv->expr = true;
 	}
 
 	set = nft_set_lookup_global(ctx->net, ctx->table,
@@ -261,6 +263,9 @@ static int nft_dynset_init(const struct nft_ctx *ctx,
 		struct nlattr *tmp;
 		int left;
 
+		if (!priv->expr)
+			return -EINVAL;
+
 		i = 0;
 		nla_for_each_nested(tmp, tb[NFTA_DYNSET_EXPRESSIONS], left) {
 			if (i == NFT_SET_EXPR_MAX) {
-- 
2.20.1

Re: [PATCH net 0/3] Netfilter fixes for net

[Jakub Kicinski]

On Sun,  3 Jan 2021 20:29:17 +0100 Pablo Neira Ayuso wrote:
> Hi Jakub, David,
> 
> The following patchset contains Netfilter fixes for net:
> 
> 1) Missing sanitization of rateest userspace string, bug has been
>    triggered by syzbot, patch from Florian Westphal.
> 
> 2) Report EOPNOTSUPP on missing set features in nft_dynset, otherwise
>    error reporting to userspace via EINVAL is misleading since this is
>    reserved for malformed netlink requests.
> 
> 3) New binaries with old kernels might silently accept several set
>    element expressions. New binaries set on the NFT_SET_EXPR and
>    NFT_DYNSET_F_EXPR flags to request for several expressions per
>    element, hence old kernels which do not support for this bail out
>    with EOPNOTSUPP.
> 
> Please, pull these changes from:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf.git

Pulled, thanks!

> P.S: Best wishes for 2021.

Happy 2021!