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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-477a973dbabsm64908285e9.3.2025.11.20.03.16.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Nov 2025 03:16:24 -0800 (PST) Date: Thu, 20 Nov 2025 11:16:23 +0000 From: David Laight To: bot+bpf-ci@kernel.org Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, dsahern@kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org, eddyz87@gmail.com, yonghong.song@linux.dev, clm@meta.com, ihor.solodrai@linux.dev Subject: Re: [PATCH 09/44] ipv6: __ip6_append_data() don't abuse max_t() casts Message-ID: <20251120111623.44ebfae7@pumpkin> In-Reply-To: References: <20251119224140.8616-10-david.laight.linux@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 20 Nov 2025 00:32:34 +0000 (UTC) bot+bpf-ci@kernel.org wrote: > > diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c > > index f904739e9..6fecf2f2c 100644 > > --- a/net/ipv6/ip6_output.c > > +++ b/net/ipv6/ip6_output.c > > @@ -1440,7 +1440,7 @@ static int __ip6_append_data(struct sock *sk, > > struct sk_buff *skb, *skb_prev = NULL; > > struct inet_cork *cork = &cork_full->base; > > struct flowi6 *fl6 = &cork_full->fl.u.ip6; > > - unsigned int maxfraglen, fragheaderlen, mtu, orig_mtu, pmtu; > > + unsigned int maxfraglen, fragheaderlen, mtu, orig_mtu; > > [ ... ] > > > @@ -1504,9 +1504,10 @@ static int __ip6_append_data(struct sock *sk, > > maxnonfragsize = mtu; > > > > if (cork->length + length > maxnonfragsize - headersize) { > > + int pmtu; > > emsgsize: > > - pmtu = max_t(int, mtu - headersize + sizeof(struct ipv6hdr), 0); > > - ipv6_local_error(sk, EMSGSIZE, fl6, pmtu); > > + pmtu = mtu - headersize + (int)sizeof(struct ipv6hdr); > > + ipv6_local_error(sk, EMSGSIZE, fl6, max(pmtu, 0)); > > return -EMSGSIZE; > > } > > Can the variable pmtu be used uninitialized here? If your AI bot doesn't understand code don't run it. David > > When reaching the emsgsize label via goto statements from earlier in > __ip6_append_data() (the checks at lines around mtu <= fragheaderlen, > headersize + transhdrlen > mtu, and the dontfrag check), the int pmtu > declaration is skipped. This leaves pmtu uninitialized when it's used > in the calculation that's passed to ipv6_local_error(). > > > --- > AI reviewed your patch. Please fix the bug or email reply why it's not a bug. > See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md > > CI run summary: https://github.com/kernel-patches/bpf/actions/runs/19519124312