net_sched: Flush gso_skb list too during ->change()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: net_sched: Flush gso_skb list too during ->change() Previously, when reducing a qdisc's limit via the ->change() operation, only the main skb queue was trimmed, potentially leaving packets in the gso_skb list. This could result in NULL pointer dereference when we only check sch->limit against sch->q.qlen. This patch introduces a new helper, qdisc_dequeue_internal(), which ensures both the gso_skb list and the main queue are properly flushed when trimming excess packets. All relevant qdiscs (codel, fq, fq_codel, fq_pie, hhf, pie) are updated to use this helper in their ->change() routines.

References

• https://git.kernel.org/stable/c/ea1132ccb112f51ba749c56a912f67970c2cd542
• https://git.kernel.org/stable/c/d3336f746f196c6a53e0480923ae93939f047b6c
• https://git.kernel.org/stable/c/d38939ebe0d992d581acb6885c1723fa83c1fb2c
• https://git.kernel.org/stable/c/a7d6e0ac0a8861f6b1027488062251a8e28150fd
• https://git.kernel.org/stable/c/d1365ca80b012d8a7863e45949e413fb61fa4861
• https://git.kernel.org/stable/c/fe88c7e4fc2c1cd75a278a15ffbf1689efad4e76
• https://git.kernel.org/stable/c/2d3cbfd6d54a2c39ce3244f33f85c595844bd7b8