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Tue, 02 Dec 2025 01:20:22 -0800 (PST) Received: from [192.168.88.32] ([212.105.155.159]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4790b0cc186sm345710215e9.13.2025.12.02.01.20.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Dec 2025 01:20:21 -0800 (PST) Message-ID: <278eb8cc-0564-4883-918e-0aaa62dfa851@redhat.com> Date: Tue, 2 Dec 2025 10:20:20 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Patch net v5 5/9] net_sched: Check the return value of qfq_choose_next_agg() To: Cong Wang , netdev@vger.kernel.org Cc: stephen@networkplumber.org, kuba@kernel.org, Xiang Mei References: <20251126195244.88124-1-xiyou.wangcong@gmail.com> <20251126195244.88124-6-xiyou.wangcong@gmail.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20251126195244.88124-6-xiyou.wangcong@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/26/25 8:52 PM, Cong Wang wrote: > qfq_choose_next_agg() could return NULL so its return value should be > properly checked unless NULL is acceptable. > > There are two cases we need to deal with: > > 1) q->in_serv_agg, which is okay with NULL since it is either checked or > just compared with other pointer without dereferencing. In fact, it > is even intentionally set to NULL in one of the cases. > > 2) in_serv_agg, which is a temporary local variable, which is not okay > with NULL, since it is dereferenced immediately, hence must be checked. > > This fix corrects one of the 2nd cases, and leaving the 1st case as they are. > > Although this bug is triggered with the netem duplicate change, the root > cause is still within qfq qdisc. Given the above, I think this patch should come first in the series WRT "net_sched: Implement the right netem duplication behavior" /P