[PATCH 5.10 270/406] netfilter: xt_u32: validate user space input

Greg Kroah-Hartman
2023-09-17T19:35:57Z

From: Wander Lairson Costa <wander@redhat.com>

commit 69c5d284f67089b4750d28ff6ac6f52ec224b330 upstream.

The xt_u32 module doesn't validate the fields in the xt_u32 structure.
An attacker may take advantage of this to trigger an OOB read by setting
the size fields with a value beyond the arrays boundaries.

Add a checkentry function to validate the structure.

This was originally reported by the ZDI project (ZDI-CAN-18408).

Fixes: 1b50b8a371e9 ("[NETFILTER]: Add u32 match")
Cc: stable@vger.kernel.org
Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netfilter/xt_u32.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

--- a/net/netfilter/xt_u32.c
+++ b/net/netfilter/xt_u32.c
@@ -96,11 +96,32 @@ static bool u32_mt(const struct sk_buff
return ret ^ data->invert;
}

+static int u32_mt_checkentry(const struct xt_mtchk_param *par)
+{
+ const struct xt_u32 *data = par->matchinfo;
+ const struct xt_u32_test *ct;
+ unsigned int i;
+
+ if (data->ntests > ARRAY_SIZE(data->tests))
+ return -EINVAL;
+
+ for (i = 0; i < data->ntests; ++i) {
+ ct = &data->tests[i];
+
+ if (ct->nnums > ARRAY_SIZE(ct->location) ||
+ ct->nvalues > ARRAY_SIZE(ct->value))
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static struct xt_match xt_u32_mt_reg __read_mostly = {
.name = "u32",
.revision = 0,
.family = NFPROTO_UNSPEC,
.match = u32_mt,
+ .checkentry = u32_mt_checkentry,
.matchsize = sizeof(struct xt_u32),
.me = THIS_MODULE,
};