[PATCH] ipv6: calipso: fix 8-bit hdrlen overflow and missing pskb_may_pull() in hop-by-hop options

[sashiko-bot at kernel.org]

> Two bugs exist in the CALIPSO hop-by-hop option handling in
> net/ipv6/calipso.c:
> 
> 1. When inserting a CALIPSO option into an existing Hop-by-Hop extension
>    header in calipso_opt_insert() or calipso_skbuff_setattr(), the
>    resulting header length `buf_len` (or `ipv6_optlen(hop) + len_delta`)
>    can exceed the maximum size representable by the 8-bit `hdrlen` field
>    (256 * 8 = 2048 bytes). When `buf_len > 2048`, `new->hdrlen = buf_len
>    / 8 - 1` (or `hop->hdrlen = ...`) truncates modulo 256, causing
>    `ipv6_optlen()` to under-report the allocated header size and
>    mismatch `opt->opt_nflen` or `skb->len`.
> 2. In calipso_skbuff_setattr(), when `ip6_hdr->nexthdr == NEXTHDR_HOP`,
>    `hop` is dereferenced at `(struct ipv6_opt_hdr *)(ip6_hdr + 1)` and
>    scanned by `calipso_opt_find(hop, &start, &end)` without ensuring
>    that the Hop-by-Hop header resides in the linear data area of `skb`
>    via `pskb_may_pull()`, risking an out-of-bounds read past `skb->tail`
>    on non-linear skbs.
> 
> Reject Hop-by-Hop headers that would exceed `8 * 256` bytes with
> `-ENOSPC`, and ensure `pskb_may_pull()` linearizes `hop` before
> inspecting it in calipso_skbuff_setattr().
> 
> Fixes: ceba1832b1b2 ("calipso: Set the calipso socket label to match the secattr.")
> Fixes: 2917f57b6bc1 ("calipso: Allow the lsm to label the skbuff directly.")
> Assisted-by: LLM
> Signed-off-by: Hui Peng <benquike at gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260919210621.3029744-1-benquike@gmail.com?part=1