--- /dev/null
+From fd94d9dadee58e09b49075240fe83423eb1dcd36 Mon Sep 17 00:00:00 2001
+From: Florian Westphal <fw@strlen.de>
+Date: Tue, 5 Sep 2023 23:13:56 +0200
+Subject: netfilter: nftables: exthdr: fix 4-byte stack OOB write
+
+From: Florian Westphal <fw@strlen.de>
+
+commit fd94d9dadee58e09b49075240fe83423eb1dcd36 upstream.
+
+If priv->len is a multiple of 4, then dst[len / 4] can write past
+the destination array which leads to stack corruption.
+
+This construct is necessary to clean the remainder of the register
+in case ->len is NOT a multiple of the register size, so make it
+conditional just like nft_payload.c does.
+
+The bug was added in 4.1 cycle and then copied/inherited when
+tcp/sctp and ip option support was added.
+
+Bug reported by Zero Day Initiative project (ZDI-CAN-21950,
+ZDI-CAN-21951, ZDI-CAN-21961).
+
+Fixes: 49499c3e6e18 ("netfilter: nf_tables: switch registers to 32 bit addressing")
+Fixes: 935b7f643018 ("netfilter: nft_exthdr: add TCP option matching")
+Fixes: 133dc203d77d ("netfilter: nft_exthdr: Support SCTP chunks")
+Fixes: dbb5281a1f84 ("netfilter: nf_tables: add support for matching IPv4 options")
+Signed-off-by: Florian Westphal <fw@strlen.de>
+Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ net/netfilter/nft_exthdr.c | 17 ++++++++++++-----
+ 1 file changed, 12 insertions(+), 5 deletions(-)
+
+--- a/net/netfilter/nft_exthdr.c
++++ b/net/netfilter/nft_exthdr.c
+@@ -33,6 +33,14 @@ static unsigned int optlen(const u8 *opt
+ return opt[offset + 1];
+ }
+
++static int nft_skb_copy_to_reg(const struct sk_buff *skb, int offset, u32 *dest, unsigned int len)
++{
++ if (len % NFT_REG32_SIZE)
++ dest[len / NFT_REG32_SIZE] = 0;
++
++ return skb_copy_bits(skb, offset, dest, len);
++}
++
+ static void nft_exthdr_ipv6_eval(const struct nft_expr *expr,
+ struct nft_regs *regs,
+ const struct nft_pktinfo *pkt)
+@@ -54,8 +62,7 @@ static void nft_exthdr_ipv6_eval(const s
+ }
+ offset += priv->offset;
+
+- dest[priv->len / NFT_REG32_SIZE] = 0;
+- if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
++ if (nft_skb_copy_to_reg(pkt->skb, offset, dest, priv->len) < 0)
+ goto err;
+ return;
+ err:
+@@ -151,8 +158,7 @@ static void nft_exthdr_ipv4_eval(const s
+ }
+ offset += priv->offset;
+
+- dest[priv->len / NFT_REG32_SIZE] = 0;
+- if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0)
++ if (nft_skb_copy_to_reg(pkt->skb, offset, dest, priv->len) < 0)
+ goto err;
+ return;
+ err:
+@@ -208,7 +214,8 @@ static void nft_exthdr_tcp_eval(const st
+ if (priv->flags & NFT_EXTHDR_F_PRESENT) {
+ *dest = 1;
+ } else {
+- dest[priv->len / NFT_REG32_SIZE] = 0;
++ if (priv->len % NFT_REG32_SIZE)
++ dest[priv->len / NFT_REG32_SIZE] = 0;
+ memcpy(dest, opt + offset, priv->len);
+ }
+