Commit b74555de authored by Eric Biggers's avatar Eric Biggers Committed by Jakub Kicinski
Browse files

llc: fix sk_buff leak in llc_conn_service() 



syzbot reported:

    BUG: memory leak
    unreferenced object 0xffff88811eb3de00 (size 224):
       comm "syz-executor559", pid 7315, jiffies 4294943019 (age 10.300s)
       hex dump (first 32 bytes):
         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
         00 a0 38 24 81 88 ff ff 00 c0 f2 15 81 88 ff ff  ..8$............
       backtrace:
         [<000000008d1c66a1>] kmemleak_alloc_recursive  include/linux/kmemleak.h:55 [inline]
         [<000000008d1c66a1>] slab_post_alloc_hook mm/slab.h:439 [inline]
         [<000000008d1c66a1>] slab_alloc_node mm/slab.c:3269 [inline]
         [<000000008d1c66a1>] kmem_cache_alloc_node+0x153/0x2a0 mm/slab.c:3579
         [<00000000447d9496>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:198
         [<000000000cdbf82f>] alloc_skb include/linux/skbuff.h:1058 [inline]
         [<000000000cdbf82f>] llc_alloc_frame+0x66/0x110 net/llc/llc_sap.c:54
         [<000000002418b52e>] llc_conn_ac_send_sabme_cmd_p_set_x+0x2f/0x140  net/llc/llc_c_ac.c:777
         [<000000001372ae17>] llc_exec_conn_trans_actions net/llc/llc_conn.c:475  [inline]
         [<000000001372ae17>] llc_conn_service net/llc/llc_conn.c:400 [inline]
         [<000000001372ae17>] llc_conn_state_process+0x1ac/0x640  net/llc/llc_conn.c:75
         [<00000000f27e53c1>] llc_establish_connection+0x110/0x170  net/llc/llc_if.c:109
         [<00000000291b2ca0>] llc_ui_connect+0x10e/0x370 net/llc/af_llc.c:477
         [<000000000f9c740b>] __sys_connect+0x11d/0x170 net/socket.c:1840
         [...]

The bug is that most callers of llc_conn_send_pdu() assume it consumes a
reference to the skb, when actually due to commit b85ab56c ("llc:
properly handle dev_queue_xmit() return value") it doesn't.

Revert most of that commit, and instead make the few places that need
llc_conn_send_pdu() to *not* consume a reference call skb_get() before.

Fixes: b85ab56c ("llc: properly handle dev_queue_xmit() return value")
Reported-by: default avatar <syzbot+6b825a6494a04cc0e3f7@syzkaller.appspotmail.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
parent c6ee11c3

include/net/llc_conn.h

+1 −1
Original line number Diff line number Diff line
@@ -104,7 +104,7 @@ void llc_sk_reset(struct sock *sk); 


/* Access to a connection */

int llc_conn_state_process(struct sock *sk, struct sk_buff *skb);

int llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb);

void llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb);

void llc_conn_rtn_pdu(struct sock *sk, struct sk_buff *skb);

void llc_conn_resend_i_pdu_as_cmd(struct sock *sk, u8 nr, u8 first_p_bit);

void llc_conn_resend_i_pdu_as_rsp(struct sock *sk, u8 nr, u8 first_f_bit);

net/llc/llc_c_ac.c

+6 −2
Original line number Diff line number Diff line
@@ -372,6 +372,7 @@ int llc_conn_ac_send_i_cmd_p_set_1(struct sock *sk, struct sk_buff *skb) 
	llc_pdu_init_as_i_cmd(skb, 1, llc->vS, llc->vR);

	rc = llc_mac_hdr_init(skb, llc->dev->dev_addr, llc->daddr.mac);

	if (likely(!rc)) {

		skb_get(skb);

		llc_conn_send_pdu(sk, skb);

		llc_conn_ac_inc_vs_by_1(sk, skb);

	}
@@ -389,7 +390,8 @@ static int llc_conn_ac_send_i_cmd_p_set_0(struct sock *sk, struct sk_buff *skb) 
	llc_pdu_init_as_i_cmd(skb, 0, llc->vS, llc->vR);

	rc = llc_mac_hdr_init(skb, llc->dev->dev_addr, llc->daddr.mac);

	if (likely(!rc)) {

		rc = llc_conn_send_pdu(sk, skb);

		skb_get(skb);

		llc_conn_send_pdu(sk, skb);

		llc_conn_ac_inc_vs_by_1(sk, skb);

	}

	return rc;
@@ -406,6 +408,7 @@ int llc_conn_ac_send_i_xxx_x_set_0(struct sock *sk, struct sk_buff *skb) 
	llc_pdu_init_as_i_cmd(skb, 0, llc->vS, llc->vR);

	rc = llc_mac_hdr_init(skb, llc->dev->dev_addr, llc->daddr.mac);

	if (likely(!rc)) {

		skb_get(skb);

		llc_conn_send_pdu(sk, skb);

		llc_conn_ac_inc_vs_by_1(sk, skb);

	}
@@ -916,7 +919,8 @@ static int llc_conn_ac_send_i_rsp_f_set_ackpf(struct sock *sk, 
	llc_pdu_init_as_i_cmd(skb, llc->ack_pf, llc->vS, llc->vR);

	rc = llc_mac_hdr_init(skb, llc->dev->dev_addr, llc->daddr.mac);

	if (likely(!rc)) {

		rc = llc_conn_send_pdu(sk, skb);

		skb_get(skb);

		llc_conn_send_pdu(sk, skb);

		llc_conn_ac_inc_vs_by_1(sk, skb);

	}

	return rc;

net/llc/llc_conn.c

+9 −23
Original line number Diff line number Diff line
@@ -30,7 +30,7 @@ 
#endif



static int llc_find_offset(int state, int ev_type);

static int llc_conn_send_pdus(struct sock *sk, struct sk_buff *skb);

static void llc_conn_send_pdus(struct sock *sk);

static int llc_conn_service(struct sock *sk, struct sk_buff *skb);

static int llc_exec_conn_trans_actions(struct sock *sk,

				       struct llc_conn_state_trans *trans,
@@ -193,11 +193,11 @@ out_skb_put: 
	return rc;

}



int llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb)

void llc_conn_send_pdu(struct sock *sk, struct sk_buff *skb)

{

	/* queue PDU to send to MAC layer */

	skb_queue_tail(&sk->sk_write_queue, skb);

	return llc_conn_send_pdus(sk, skb);

	llc_conn_send_pdus(sk);

}



/**
@@ -255,7 +255,7 @@ void llc_conn_resend_i_pdu_as_cmd(struct sock *sk, u8 nr, u8 first_p_bit) 
	if (howmany_resend > 0)

		llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;

	/* any PDUs to re-send are queued up; start sending to MAC */

	llc_conn_send_pdus(sk, NULL);

	llc_conn_send_pdus(sk);

out:;

}
@@ -296,7 +296,7 @@ void llc_conn_resend_i_pdu_as_rsp(struct sock *sk, u8 nr, u8 first_f_bit) 
	if (howmany_resend > 0)

		llc->vS = (llc->vS + 1) % LLC_2_SEQ_NBR_MODULO;

	/* any PDUs to re-send are queued up; start sending to MAC */

	llc_conn_send_pdus(sk, NULL);

	llc_conn_send_pdus(sk);

out:;

}
@@ -340,16 +340,12 @@ out: 
/**

 *	llc_conn_send_pdus - Sends queued PDUs

 *	@sk: active connection

 *	@hold_skb: the skb held by caller, or NULL if does not care

 *

 *	Sends queued pdus to MAC layer for transmission. When @hold_skb is

 *	NULL, always return 0. Otherwise, return 0 if @hold_skb is sent

 *	successfully, or 1 for failure.

 *	Sends queued pdus to MAC layer for transmission.

 */

static int llc_conn_send_pdus(struct sock *sk, struct sk_buff *hold_skb)

static void llc_conn_send_pdus(struct sock *sk)

{

	struct sk_buff *skb;

	int ret = 0;



	while ((skb = skb_dequeue(&sk->sk_write_queue)) != NULL) {

		struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
@@ -361,20 +357,10 @@ static int llc_conn_send_pdus(struct sock *sk, struct sk_buff *hold_skb) 
			skb_queue_tail(&llc_sk(sk)->pdu_unack_q, skb);

			if (!skb2)

				break;

			dev_queue_xmit(skb2);

		} else {

			bool is_target = skb == hold_skb;

			int rc;



			if (is_target)

				skb_get(skb);

			rc = dev_queue_xmit(skb);

			if (is_target)

				ret = rc;

			skb = skb2;

		}

		dev_queue_xmit(skb);

	}



	return ret;

}



/**

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