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Miller" , Jakub Kicinski , Paolo Abeni , Peter Oskolkov , open list Subject: Re: [PATTCH net v5 6/8] net/sched: netem: null-terminate tfifo linear queue tail Message-ID: <20260411075101.05c2d8b3@phoenix.local> In-Reply-To: References: <20260411051700.311679-1-stephen@networkplumber.org> <20260411051700.311679-7-stephen@networkplumber.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Fri, 10 Apr 2026 23:38:08 -0700 Eric Dumazet wrote: > On Fri, Apr 10, 2026 at 10:17=E2=80=AFPM Stephen Hemminger > wrote: > > > > When tfifo_enqueue() appends a packet to the linear queue tail, > > nskb->next is never set to NULL. The list terminates correctly > > only by accident if the skb arrived with next already NULL. > > > > Explicitly null-terminate the tail to prevent list corruption. > > > > Fixes: d66280b12bd7 ("net: netem: use a list in addition to rbtree") > > Signed-off-by: Stephen Hemminger > > Reviewed-by: Simon Horman =20 >=20 > Can you explain how skb->next could be not NULL ? >=20 > This would be a bug in the upper stack. >=20 > Only TCQ_F_NOLOCK qdiscs (pfifo_fast) can possibly get such skbs, and > it would not care. >=20 > Other qdiscs already get skbs with skb_mark_not_on_list(skb). Thanks, this patch came from a false positive from one of the review prompts. Dropping it.