Re: [PATCH net-next 2/2] net: pull headers in qdisc_pkt_len_segs_init()

[Joe Damato <joe@dama.to>]

On Fri, Apr 03, 2026 at 10:15:40PM +0000, Eric Dumazet wrote:
> Most ndo_start_xmit() methods expects headers of gso packets
> to be already in skb->head.
> 
> net/core/tso.c users are particularly at risk, because tso_build_hdr()
> does a memcpy(hdr, skb->data, hdr_len);
> 
> qdisc_pkt_len_segs_init() already does a dissection of gso packets.
> 
> Use pskb_may_pull() instead of skb_header_pointer() to make
> sure drivers do not have to reimplement this.
> 
> Some malicious packets could be fed, detect them so that we can
> drop them sooner with a new SKB_DROP_REASON_SKB_BAD_GSO drop_reason.
> 
> Fixes: e876f208af18 ("net: Add a software TSO helper API")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  include/net/dropreason-core.h |  3 +++
>  net/core/dev.c                | 51 +++++++++++++++++++++--------------
>  2 files changed, 34 insertions(+), 20 deletions(-)
> 

Reviewed-by: Joe Damato <joe@dama.to>