[PATCH net v2] cipso: adjust cached option offsets when removing CIPSO

[sashiko-bot at kernel.org]

> cipso_v4_skbuff_delattr() removes the CIPSO bytes but does not adjust
> cached offsets for options that follow them.
> 
> For example, with a valid 10-byte CIPSO option followed by a seven-byte
> RR option, parsing records rr at offset 30.  Removing CIPSO moves RR to
> offset 20, while the cached offset remains 30.  Consumers such as
> ip_forward_options() and __ip_options_echo() then access the wrong bytes;
> the latter may interpret packet data as the option length and copy it into
> fixed-size option storage.
> 
> Mirror cipso_v4_delopt() and subtract cipso_len from the srr, rr, ts and
> router_alert offsets when they follow CIPSO.  cipso_len is the distance
> the first memmove() shifts those options.  The later header move and
> network-header reset relocate the bytes and their offset base together.
> 
> Fixes: 89aa3619d141 ("cipso: make cipso_v4_skbuff_delattr() fully remove the CIPSO options")
> Cc: stable at vger.kernel.org
> Reviewed-by: Ondrej Mosnáček <omosnacek at gmail.com>
> Assisted-by: LLM
> Signed-off-by: Daehyeon Ko <4ncienth at gmail.com>

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

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Sashiko AI review · https://sashiko.dev/#/patchset/20261006035108.3101440-1-4ncienth@gmail.com?part=1