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[73.241.150.58]) by smtp.gmail.com with ESMTPSA id s33sm803136pfg.18.2021.10.27.12.20.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Oct 2021 12:20:05 -0700 (PDT) Subject: Re: [PATCH net] net: gro: set the last skb->next to NULL when it get merged To: kerneljasonxing@gmail.com, davem@davemloft.net, kuba@kernel.org, alobakin@pm.me, jonathan.lemon@gmail.com, willemb@google.com, pabeni@redhat.com, vvs@virtuozzo.com, cong.wang@bytedance.com Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Jason Xing References: <20211026131859.59114-1-kerneljasonxing@gmail.com> From: Eric Dumazet Message-ID: <2b839087-ed6a-d498-e1ab-c6bcea2f2965@gmail.com> Date: Wed, 27 Oct 2021 12:20:04 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20211026131859.59114-1-kerneljasonxing@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/26/21 6:18 AM, kerneljasonxing@gmail.com wrote: > From: Jason Xing > > Setting the @next of the last skb to NULL to prevent the panic in future > when someone does something to the last of the gro list but its @next is > invalid. > > For example, without the fix (commit: ece23711dd95), a panic could happen > with the clsact loaded when skb is redirected and then validated in > validate_xmit_skb_list() which could access the error addr of the @next > of the last skb. Thus, "general protection fault" would appear after that. > If this a bug, please provide a Fixes: tag > Signed-off-by: Jason Xing > --- > net/core/skbuff.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 2170bea..7b248f1 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -4396,6 +4396,7 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb) > skb_shinfo(p)->frag_list = skb; > else > NAPI_GRO_CB(p)->last->next = skb; > + skb->next = NULL; Really at this point skb->next must be already NULL. Please provide a stack trace so that we fix the caller instead of adding more code in GRO layer. > NAPI_GRO_CB(p)->last = skb; > __skb_header_release(skb); > lp = p; >