Re: [PATCH ipsec v2 1/7] xfrm: esp6: use the current sequence number for the IV

[sashiko-bot@kernel.org]

> When a GSO packet is split in software for IPv6 ESP,
> validate_xmit_xfrm() calls esp6_xmit() for each segment. These
> segments have XFRM_GSO_SEGMENT set, but after the split, skb_is_gso()
> returns false for each skb, so each call increments xo->seq.low by one
> after writing the ESP sequence number.
> 
> When encryption is done in software, the AES-GCM IV is generated from
> the incremented value: if the last segment has sequence number 100, it
> uses 101 to generate its IV. A bug arises when the next ordinary
> packet is processed: it also goes through esp6_xmit() with sequence
> number 101, but since it does not have XFRM_GSO_SEGMENT, no increment
> happens and the same IV is reused.
> 
> Save the full sequence number before incrementing xo->seq, and use
> that value to generate the IV.
> 
> Fixes: 3dca3f38cfb8 ("xfrm: Separate ESP handling from segmentation for GRO packets.")
> Cc: stable@vger.kernel.org
> Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261108142652.1330952-1-Jeremy.Jean@oss.cyber.gouv.fr?part=1