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Wed, 22 Apr 2026 09:31:34 -0700 (PDT) Received: from localhost ([2a03:2880:12ff:74::]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7dcd164d2c3sm5895751a34.24.2026.04.22.09.31.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Apr 2026 09:31:34 -0700 (PDT) Date: Wed, 22 Apr 2026 09:31:33 -0700 Message-ID: From: Stanislav Fomichev To: Jason Xing Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, Jason Xing In-Reply-To: <20260422033650.68457-6-kerneljasonxing@gmail.com> Subject: Re: [PATCH net v3 5/8] xsk: avoid skb leak in XDP_TX_METADATA case Content-Type: text/plain Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: > From: Jason Xing > > Fix it by explicitly adding kfree_skb() before returning back to its > caller. > > How to reproduce it in virtio_net: > 1. the current skb is the first one (which means no frag and xs->skb is > NULL) and users enable metadata feature. > 2. xsk_skb_metadata() returns a error code. > 3. the caller xsk_build_skb() clears skb by using 'skb = NULL;'. > 4. there is no chance to free this skb anymore. > > Closes: https://lore.kernel.org/all/20260415085204.3F87AC19424@smtp.kernel.org/ > Fixes: 30c3055f9c0d ("xsk: wrap generic metadata handling onto separate function") > Signed-off-by: Jason Xing > --- > net/xdp/xsk.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c > index 88ec6d2cbbcf..c49b58199d2f 100644 > --- a/net/xdp/xsk.c > +++ b/net/xdp/xsk.c > @@ -741,8 +741,10 @@ static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs, > skb_reserve(skb, hr); > if (desc->options & XDP_TX_METADATA) { > err = xsk_skb_metadata(skb, buffer, desc, pool, hr); > - if (unlikely(err)) > + if (unlikely(err)) { > + kfree_skb(skb); > return ERR_PTR(err); > + } > } > } else { > struct xsk_addrs *xsk_addr; > -- > 2.41.3 > Acked-by: Stanislav Fomichev