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b=0OCrF9SPjgMnAlrDvip9JHtYAXepPyIMRDfWLatFrQq75HbZUI8wFvBR6j3uIo7Zl89oAW J+r+HHHwMluaKnCA== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 54EC713693; Tue, 28 Oct 2025 16:34:59 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id TmCpEbPwAGncHQAAD6G6ig (envelope-from ); Tue, 28 Oct 2025 16:34:59 +0000 Message-ID: Date: Tue, 28 Oct 2025 17:34:46 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2 bpf] xsk: avoid data corruption on cq descriptor number To: bpf@vger.kernel.org Cc: netdev@vger.kernel.org, magnus.karlsson@intel.com, maciej.fijalkowski@intel.com, sdf@fomichev.me, kerneljasonxing@gmail.com, fw@strlen.de References: <20251028160200.4204-1-fmancera@suse.de> <20251028160200.4204-2-fmancera@suse.de> Content-Language: en-US From: Fernando Fernandez Mancera In-Reply-To: <20251028160200.4204-2-fmancera@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Level: X-Spam-Flag: NO X-Rspamd-Queue-Id: C0BB3218DF X-Rspamd-Action: no action X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:mid,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; MID_RHS_MATCH_FROM(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[vger.kernel.org,intel.com,fomichev.me,gmail.com,strlen.de]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_NONE(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Spam-Score: -4.51 On 10/28/25 5:02 PM, Fernando Fernandez Mancera wrote: > Since commit 30f241fcf52a ("xsk: Fix immature cq descriptor > production"), the descriptor number is stored in skb control block and > xsk_cq_submit_addr_locked() relies on it to put the umem addrs onto > pool's completion queue. >[...] > > len = desc->len; > @@ -804,6 +823,11 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, > if (unlikely(err)) > goto free_err; > > + if (!skb_ext_add(skb, SKB_EXT_XDP)) { > + err = -ENOMEM; > + goto free_err; > + } > + This is a leftover. Without it, the logic simplified and indeed the performance for non-fragmented traffic is not affected at all. While reviewing this, consider this line is dropped. I will send a V2 in 24 hours anyway as this is indeed introducing a buggy behavior. > xsk_skb_init_misc(skb, xs, desc->addr); > if (desc->options & XDP_TX_METADATA) { > err = xsk_skb_metadata(skb, buffer, desc, > @@ -814,6 +838,7 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, > } else { > int nr_frags = skb_shinfo(skb)->nr_frags; > struct xsk_addr_node *xsk_addr; > + struct xdp_skb_ext *ext; > struct page *page; > u8 *vaddr; > > @@ -828,6 +853,22 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, > goto free_err; > } > > + ext = skb_ext_find(skb, SKB_EXT_XDP); > + if (!ext) { > + ext = skb_ext_add(skb, SKB_EXT_XDP); > + if (!ext) { > + __free_page(page); > + err = -ENOMEM; > + goto free_err; > + } > + memset(ext, 0, sizeof(*ext)); > + INIT_LIST_HEAD(&ext->addrs_list); > + ext->num_descs = 1; > + } else if (ext->num_descs == 0) { > + INIT_LIST_HEAD(&ext->addrs_list); > + ext->num_descs = 1; > + } > + > xsk_addr = kmem_cache_zalloc(xsk_tx_generic_cache, GFP_KERNEL); > if (!xsk_addr) { > __free_page(page); > @@ -843,12 +884,11 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, > refcount_add(PAGE_SIZE, &xs->sk.sk_wmem_alloc); > > xsk_addr->addr = desc->addr; > - list_add_tail(&xsk_addr->addr_node, &XSKCB(skb)->addrs_list); > + list_add_tail(&xsk_addr->addr_node, &ext->addrs_list); > + xsk_inc_num_desc(skb); > } > } > > - xsk_inc_num_desc(skb); > - > return skb; > > free_err: > @@ -857,7 +897,6 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, > > if (err == -EOVERFLOW) { > /* Drop the packet */ > - xsk_inc_num_desc(xs->skb); > xsk_drop_skb(xs->skb); > xskq_cons_release(xs->tx); > } else {