llc: fix sk_buff leak in llc_sap_state_process() (c6ee11c3) · Commits · 戴 / test

syzbot reported: BUG: memory leak unreferenced object 0xffff888116270800 (size 224): comm "syz-executor641", pid 7047, jiffies 4294947360 (age 13.860s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 20 e1 2a 81 88 ff ff 00 40 3d 2a 81 88 ff ff . .*.....@=*.... backtrace: [<000000004d41b4cc>] kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline] [<000000004d41b4cc>] slab_post_alloc_hook mm/slab.h:439 [inline] [<000000004d41b4cc>] slab_alloc_node mm/slab.c:3269 [inline] [<000000004d41b4cc>] kmem_cache_alloc_node+0x153/0x2a0 mm/slab.c:3579 [<00000000506a5965>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:198 [<000000001ba5a161>] alloc_skb include/linux/skbuff.h:1058 [inline] [<000000001ba5a161>] alloc_skb_with_frags+0x5f/0x250 net/core/skbuff.c:5327 [<0000000047d9c78b>] sock_alloc_send_pskb+0x269/0x2a0 net/core/sock.c:2225 [<000000003828fe54>] sock_alloc_send_skb+0x32/0x40 net/core/sock.c:2242 [<00000000e34d94f9>] llc_ui_sendmsg+0x10a/0x540 net/llc/af_llc.c:933 [<00000000de2de3fb>] sock_sendmsg_nosec net/socket.c:652 [inline] [<00000000de2de3fb>] sock_sendmsg+0x54/0x70 net/socket.c:671 [<000000008fe16e7a>] __sys_sendto+0x148/0x1f0 net/socket.c:1964 [...] The bug is that llc_sap_state_process() always takes an extra reference to the skb, but sometimes neither llc_sap_next_state() nor llc_sap_state_process() itself drops this reference. Fix it by changing llc_sap_next_state() to never consume a reference to the skb, rather than sometimes do so and sometimes not. Then remove the extra skb_get() and kfree_skb() from llc_sap_state_process(). Reported-by:

<syzbot+6bf095f9becf5efef645@syzkaller.appspotmail.com> Reported-by:

<syzbot+31c16aa4202dace3812e@syzkaller.appspotmail.com> Fixes: ("Linux-2.6.12-rc2") Signed-off-by:

Eric Biggers <ebiggers@google.com> Signed-off-by:

Jakub Kicinski <jakub.kicinski@netronome.com>

net/llc/llc_s_ac.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -58,8 +58,10 @@ int llc_sap_action_send_ui(struct llc_sap sap, struct sk_buff skb)
		ev->daddr.lsap, LLC_PDU_CMD);
		llc_pdu_init_as_ui_cmd(skb);
		rc = llc_mac_hdr_init(skb, ev->saddr.mac, ev->daddr.mac);
		if (likely(!rc))
		if (likely(!rc)) {
		skb_get(skb);
		rc = dev_queue_xmit(skb);
		}
		return rc;
		}

		@@ -81,8 +83,10 @@ int llc_sap_action_send_xid_c(struct llc_sap sap, struct sk_buff skb)
		ev->daddr.lsap, LLC_PDU_CMD);
		llc_pdu_init_as_xid_cmd(skb, LLC_XID_NULL_CLASS_2, 0);
		rc = llc_mac_hdr_init(skb, ev->saddr.mac, ev->daddr.mac);
		if (likely(!rc))
		if (likely(!rc)) {
		skb_get(skb);
		rc = dev_queue_xmit(skb);
		}
		return rc;
		}

		@@ -135,8 +139,10 @@ int llc_sap_action_send_test_c(struct llc_sap sap, struct sk_buff skb)
		ev->daddr.lsap, LLC_PDU_CMD);
		llc_pdu_init_as_test_cmd(skb);
		rc = llc_mac_hdr_init(skb, ev->saddr.mac, ev->daddr.mac);
		if (likely(!rc))
		if (likely(!rc)) {
		skb_get(skb);
		rc = dev_queue_xmit(skb);
		}
		return rc;
		}

net/llc/llc_sap.c

+8 −15

Original line number	Diff line number	Diff line
		@@ -197,29 +197,22 @@ out:
		* After executing actions of the event, upper layer will be indicated
		* if needed(on receiving an UI frame). sk can be null for the
		* datalink_proto case.
		*
		* This function always consumes a reference to the skb.
		*/
		static void llc_sap_state_process(struct llc_sap sap, struct sk_buff skb)
		{
		struct llc_sap_state_ev *ev = llc_sap_ev(skb);

		/*
		* We have to hold the skb, because llc_sap_next_state
		* will kfree it in the sending path and we need to
		* look at the skb->cb, where we encode llc_sap_state_ev.
		*/
		skb_get(skb);
		ev->ind_cfm_flag = 0;
		llc_sap_next_state(sap, skb);
		if (ev->ind_cfm_flag == LLC_IND) {
		if (skb->sk->sk_state == TCP_LISTEN)
		kfree_skb(skb);
		else {

		if (ev->ind_cfm_flag == LLC_IND && skb->sk->sk_state != TCP_LISTEN) {
		llc_save_primitive(skb->sk, skb, ev->prim);

		/* queue skb to the user. */
		if (sock_queue_rcv_skb(skb->sk, skb))
		kfree_skb(skb);
		}
		if (sock_queue_rcv_skb(skb->sk, skb) == 0)
		return;
		}
		kfree_skb(skb);
		}

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