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a469feed39
Add a regression test for the NULL pointer dereference fixed in the previous commit. Before the fix, taprio_graft() stored NULL into q->qdiscs[cl - 1] when an explicitly grafted child qdisc was deleted via RTM_DELQDISC; the next RTM_GETTCLASS dump then crashed the kernel in taprio_dump_class() while reading child->handle. The test installs a taprio root qdisc on a multi-queue netdevsim device, grafts a pfifo child onto class 8001:1, deletes that child, and then performs a class dump. On a fixed kernel the dump succeeds and all eight taprio classes are listed; on an unpatched kernel the class dump crashes, which surfaces as a test failure. Signed-off-by: Weiming Shi <bestswngs@gmail.com> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Link: https://patch.msgid.link/20260422161958.2517539-4-bestswngs@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>