Subject: Re: [PATCH bpf 2/3] bpf, sockmap: on cleanup we additionally need to remove cached skb

From: Dan Carpenter <[email-masked]>
Date: Wed, 21 Jul 2021 12:38:11 +0300

Hi John,

url:    https://github.com/0day-ci/linux/commits/John-Fastabend/sockmap-fixes-picked-up-by-stress-tests/20210720-144138
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git master
config: i386-randconfig-m021-20210720 (attached as .config)
compiler: gcc-10 (Ubuntu 10.3.0-1ubuntu1~20.04) 10.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[email-masked]>
Reported-by: Dan Carpenter <[email-masked]>

smatch warnings:
net/core/skmsg.c:627 sk_psock_backlog() error: uninitialized symbol 'skb'.
net/core/skmsg.c:639 sk_psock_backlog() error: uninitialized symbol 'off'.
net/core/skmsg.c:640 sk_psock_backlog() error: uninitialized symbol 'len'.

vim +/skb +627 net/core/skmsg.c

604326b41a6fb9 Daniel Borkmann 2018-10-13  609  static void sk_psock_backlog(struct work_struct *work)
604326b41a6fb9 Daniel Borkmann 2018-10-13  610  {
604326b41a6fb9 Daniel Borkmann 2018-10-13  611  	struct sk_psock *psock = container_of(work, struct sk_psock, work);
604326b41a6fb9 Daniel Borkmann 2018-10-13  612  	struct sk_psock_work_state *state = &psock->work_state;
604326b41a6fb9 Daniel Borkmann 2018-10-13  613  	struct sk_buff *skb;
604326b41a6fb9 Daniel Borkmann 2018-10-13  614  	bool ingress;
604326b41a6fb9 Daniel Borkmann 2018-10-13  615  	u32 len, off;
604326b41a6fb9 Daniel Borkmann 2018-10-13  616  	int ret;
604326b41a6fb9 Daniel Borkmann 2018-10-13  617  
799aa7f98d53e0 Cong Wang       2021-03-30  618  	mutex_lock(&psock->work_mutex);
d1f6b1c794e27f John Fastabend  2021-07-19  619  	if (unlikely(state->skb)) {
d1f6b1c794e27f John Fastabend  2021-07-19  620  		spin_lock_bh(&psock->ingress_lock);
604326b41a6fb9 Daniel Borkmann 2018-10-13  621  		skb = state->skb;
604326b41a6fb9 Daniel Borkmann 2018-10-13  622  		len = state->len;
604326b41a6fb9 Daniel Borkmann 2018-10-13  623  		off = state->off;
604326b41a6fb9 Daniel Borkmann 2018-10-13  624  		state->skb = NULL;
d1f6b1c794e27f John Fastabend  2021-07-19  625  		spin_unlock_bh(&psock->ingress_lock);
604326b41a6fb9 Daniel Borkmann 2018-10-13  626  	}

skb uninitialized on else path.

d1f6b1c794e27f John Fastabend  2021-07-19 @627  	if (skb)
d1f6b1c794e27f John Fastabend  2021-07-19  628  		goto start;
604326b41a6fb9 Daniel Borkmann 2018-10-13  629  
604326b41a6fb9 Daniel Borkmann 2018-10-13  630  	while ((skb = skb_dequeue(&psock->ingress_skb))) {
604326b41a6fb9 Daniel Borkmann 2018-10-13  631  		len = skb->len;
604326b41a6fb9 Daniel Borkmann 2018-10-13  632  		off = 0;
604326b41a6fb9 Daniel Borkmann 2018-10-13  633  start:
e3526bb92a2084 Cong Wang       2021-02-23  634  		ingress = skb_bpf_ingress(skb);
e3526bb92a2084 Cong Wang       2021-02-23  635  		skb_bpf_redirect_clear(skb);
604326b41a6fb9 Daniel Borkmann 2018-10-13  636  		do {
604326b41a6fb9 Daniel Borkmann 2018-10-13  637  			ret = -EIO;
799aa7f98d53e0 Cong Wang       2021-03-30  638  			if (!sock_flag(psock->sk, SOCK_DEAD))
604326b41a6fb9 Daniel Borkmann 2018-10-13 @639  				ret = sk_psock_handle_skb(psock, skb, off,
604326b41a6fb9 Daniel Borkmann 2018-10-13 @640  							  len, ingress);
604326b41a6fb9 Daniel Borkmann 2018-10-13  641  			if (ret <= 0) {
604326b41a6fb9 Daniel Borkmann 2018-10-13  642  				if (ret == -EAGAIN) {
d1f6b1c794e27f John Fastabend  2021-07-19  643  					sk_psock_skb_state(psock, state, skb,
d1f6b1c794e27f John Fastabend  2021-07-19  644  							   len, off);
604326b41a6fb9 Daniel Borkmann 2018-10-13  645  					goto end;
604326b41a6fb9 Daniel Borkmann 2018-10-13  646  				}
604326b41a6fb9 Daniel Borkmann 2018-10-13  647  				/* Hard errors break pipe and stop xmit. */
604326b41a6fb9 Daniel Borkmann 2018-10-13  648  				sk_psock_report_error(psock, ret ? -ret : EPIPE);
604326b41a6fb9 Daniel Borkmann 2018-10-13  649  				sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED);
781dd0431eb549 Cong Wang       2021-06-14  650  				sock_drop(psock->sk, skb);
604326b41a6fb9 Daniel Borkmann 2018-10-13  651  				goto end;
604326b41a6fb9 Daniel Borkmann 2018-10-13  652  			}
604326b41a6fb9 Daniel Borkmann 2018-10-13  653  			off += ret;
604326b41a6fb9 Daniel Borkmann 2018-10-13  654  			len -= ret;
604326b41a6fb9 Daniel Borkmann 2018-10-13  655  		} while (len);
604326b41a6fb9 Daniel Borkmann 2018-10-13  656  
604326b41a6fb9 Daniel Borkmann 2018-10-13  657  		if (!ingress)
604326b41a6fb9 Daniel Borkmann 2018-10-13  658  			kfree_skb(skb);
604326b41a6fb9 Daniel Borkmann 2018-10-13  659  	}
604326b41a6fb9 Daniel Borkmann 2018-10-13  660  end:
799aa7f98d53e0 Cong Wang       2021-03-30  661  	mutex_unlock(&psock->work_mutex);
604326b41a6fb9 Daniel Borkmann 2018-10-13  662  }

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