Re: [PATCH] xfrm: iptfs: validate inner IPv4 header length in IPTFS payload

[Steffen Klassert]

On Sun, Mar 01, 2026 at 10:56:38AM +0000, Roshan Kumar wrote:
> 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@xxxxxxxxx>
> Fixes: 6c82d2433671 ("xfrm: iptfs: add basic receive packet (tunnel egress) handling")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Roshan Kumar <roshaen09@xxxxxxxxx>

Applied to the ipsec tree, thanks a lot!