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xfrm: iptfs: validate inner IPv4 header length in IPTFS payload

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Add validation of the inner IPv4 packet tot_len and ihl fields parsed
from decrypted IPTFS payloads in __input_process_payload(). A crafted
ESP packet containing an inner IPv4 header with tot_len=0 causes an
infinite loop: iplen=0 leads to capturelen=min(0, remaining)=0, so the
data offset never advances and the while(data < tail) loop never
terminates, spinning forever in softirq context.

Reject inner IPv4 packets where tot_len < ihl*4 or ihl*4 < sizeof(struct
iphdr), which catches both the tot_len=0 case and malformed ihl values.
The normal IP stack performs this validation in ip_rcv_core(), but IPTFS
extracts and processes inner packets before they reach that layer.

Reported-by: Roshan Kumar <roshaen09@gmail.com>
Fixes: 6c82d24336 ("xfrm: iptfs: add basic receive packet (tunnel egress) handling")
Cc: stable@vger.kernel.org
Signed-off-by: Roshan Kumar <roshaen09@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Roshan Kumar 2026-03-01 10:56:38 +00:00 committed by Steffen Klassert
parent 0c0eef8ccd
commit 0d10393d5e
1 changed files with 5 additions and 0 deletions
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5
net/xfrm/xfrm_iptfs.c
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@ -991,6 +991,11 @@ static bool __input_process_payload(struct xfrm_state *x, u32 data,
iplen = be16_to_cpu(iph->tot_len);
iphlen = iph->ihl << 2;
if (iplen < iphlen || iphlen < sizeof(*iph)) {
XFRM_INC_STATS(net,
LINUX_MIB_XFRMINHDRERROR);
goto done;
}
protocol = cpu_to_be16(ETH_P_IP);
XFRM_MODE_SKB_CB(skbseq->root_skb)->tos = iph->tos;
} else if (iph->version == 0x6) {