Re: net/dccp: use-after-free in dccp_feat_activate_values
From: Eric Dumazet <hidden>
Date: 2017-03-03 16:08:42
Also in:
lkml
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
On Fri, 2017-03-03 at 07:22 -0800, Eric Dumazet wrote:
On Fri, Mar 3, 2017 at 7:12 AM, Dmitry Vyukov [off-list ref] wrote:quoted
The first bot that picked this up started spewing: BUG: spinlock recursion on CPU#1, syz-executor2/9452Yes. The bug is not about locking the listener, but protecting fields of struct dccp_request_sock I will provide a patch, once I reach the office and after the breakfast ;)
OK here is what I suggest to fix the races.
diff --git a/include/linux/dccp.h b/include/linux/dccp.h
index 61d042bbbf607253033d9948b291cab2322814ba..68449293c4b6233c1a1d4133b1819376a9310225 100644
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h@@ -163,6 +163,7 @@ struct dccp_request_sock { __u64 dreq_isr; __u64 dreq_gsr; __be32 dreq_service; + spinlock_t dreq_lock; struct list_head dreq_featneg; __u32 dreq_timestamp_echo; __u32 dreq_timestamp_time;
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index e267e6f4c9a5566b369a03a600a408e5bd41cbad..abd07a443219853b022bef41cb072e90ff8f07f0 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c@@ -142,6 +142,13 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb, struct dccp_request_sock *dreq = dccp_rsk(req); bool own_req; + /* TCP/DCCP listeners became lockless. + * DCCP stores complex state in its request_sock, so we need + * a protection for them, now this code runs without being protected + * by the parent (listener) lock. + */ + spin_lock_bh(&dreq->dreq_lock); + /* Check for retransmitted REQUEST */ if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
@@ -156,7 +163,7 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb, inet_rtx_syn_ack(sk, req); } /* Network Duplicate, discard packet */ - return NULL; + goto out; } DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
@@ -182,20 +189,20 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb, child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL, req, &own_req); - if (!child) - goto listen_overflow; - - return inet_csk_complete_hashdance(sk, child, req, own_req); + if (child) { + child = inet_csk_complete_hashdance(sk, child, req, own_req); + goto out; + } -listen_overflow: - dccp_pr_debug("listen_overflow!\n"); DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY; drop: if (dccp_hdr(skb)->dccph_type != DCCP_PKT_RESET) req->rsk_ops->send_reset(sk, skb); inet_csk_reqsk_queue_drop(sk, req); - return NULL; +out: + spin_unlock_bh(&dreq->dreq_lock); + return child; } EXPORT_SYMBOL_GPL(dccp_check_req);
@@ -246,6 +253,7 @@ int dccp_reqsk_init(struct request_sock *req, { struct dccp_request_sock *dreq = dccp_rsk(req); + spin_lock_init(&dreq->dreq_lock); inet_rsk(req)->ir_rmt_port = dccp_hdr(skb)->dccph_sport; inet_rsk(req)->ir_num = ntohs(dccp_hdr(skb)->dccph_dport); inet_rsk(req)->acked = 0;