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Commit f1712c73 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

can: Fix kernel panic at security_sock_rcv_skb 



Zhang Yanmin reported crashes [1] and provided a patch adding a
synchronize_rcu() call in can_rx_unregister()

The main problem seems that the sockets themselves are not RCU
protected.

If CAN uses RCU for delivery, then sockets should be freed only after
one RCU grace period.

Recent kernels could use sock_set_flag(sk, SOCK_RCU_FREE), but let's
ease stable backports with the following fix instead.

[1]
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff81495e25>] selinux_socket_sock_rcv_skb+0x65/0x2a0

Call Trace:
 <IRQ>
 [<ffffffff81485d8c>] security_sock_rcv_skb+0x4c/0x60
 [<ffffffff81d55771>] sk_filter+0x41/0x210
 [<ffffffff81d12913>] sock_queue_rcv_skb+0x53/0x3a0
 [<ffffffff81f0a2b3>] raw_rcv+0x2a3/0x3c0
 [<ffffffff81f06eab>] can_rcv_filter+0x12b/0x370
 [<ffffffff81f07af9>] can_receive+0xd9/0x120
 [<ffffffff81f07beb>] can_rcv+0xab/0x100
 [<ffffffff81d362ac>] __netif_receive_skb_core+0xd8c/0x11f0
 [<ffffffff81d36734>] __netif_receive_skb+0x24/0xb0
 [<ffffffff81d37f67>] process_backlog+0x127/0x280
 [<ffffffff81d36f7b>] net_rx_action+0x33b/0x4f0
 [<ffffffff810c88d4>] __do_softirq+0x184/0x440
 [<ffffffff81f9e86c>] do_softirq_own_stack+0x1c/0x30
 <EOI>
 [<ffffffff810c76fb>] do_softirq.part.18+0x3b/0x40
 [<ffffffff810c8bed>] do_softirq+0x1d/0x20
 [<ffffffff81d30085>] netif_rx_ni+0xe5/0x110
 [<ffffffff8199cc87>] slcan_receive_buf+0x507/0x520
 [<ffffffff8167ef7c>] flush_to_ldisc+0x21c/0x230
 [<ffffffff810e3baf>] process_one_work+0x24f/0x670
 [<ffffffff810e44ed>] worker_thread+0x9d/0x6f0
 [<ffffffff810e4450>] ? rescuer_thread+0x480/0x480
 [<ffffffff810ebafc>] kthread+0x12c/0x150
 [<ffffffff81f9ccef>] ret_from_fork+0x3f/0x70

Reported-by: default avatarZhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarOliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dc97a89e

include/linux/can/core.h

+3 −4
Original line number Diff line number Diff line
@@ -45,10 +45,9 @@ struct can_proto { 
extern int  can_proto_register(const struct can_proto *cp);

extern void can_proto_unregister(const struct can_proto *cp);



extern int  can_rx_register(struct net_device *dev, canid_t can_id,

			    canid_t mask,

int can_rx_register(struct net_device *dev, canid_t can_id, canid_t mask,

		    void (*func)(struct sk_buff *, void *),

			    void *data, char *ident);

		    void *data, char *ident, struct sock *sk);



extern void can_rx_unregister(struct net_device *dev, canid_t can_id,

			      canid_t mask,

net/can/af_can.c

+10 −2
Original line number Diff line number Diff line
@@ -445,6 +445,7 @@ static struct hlist_head *find_rcv_list(canid_t *can_id, canid_t *mask, 
 * @func: callback function on filter match

 * @data: returned parameter for callback function

 * @ident: string for calling module identification

 * @sk: socket pointer (might be NULL)

 *

 * Description:

 *  Invokes the callback function with the received sk_buff and the given
@@ -468,7 +469,7 @@ static struct hlist_head *find_rcv_list(canid_t *can_id, canid_t *mask, 
 */

int can_rx_register(struct net_device *dev, canid_t can_id, canid_t mask,

		    void (*func)(struct sk_buff *, void *), void *data,

		    char *ident)

		    char *ident, struct sock *sk)

{

	struct receiver *r;

	struct hlist_head *rl;
@@ -496,6 +497,7 @@ int can_rx_register(struct net_device *dev, canid_t can_id, canid_t mask, 
		r->func    = func;

		r->data    = data;

		r->ident   = ident;

		r->sk      = sk;



		hlist_add_head_rcu(&r->list, rl);

		d->entries++;
@@ -520,8 +522,11 @@ EXPORT_SYMBOL(can_rx_register); 
static void can_rx_delete_receiver(struct rcu_head *rp)

{

	struct receiver *r = container_of(rp, struct receiver, rcu);

	struct sock *sk = r->sk;



	kmem_cache_free(rcv_cache, r);

	if (sk)

		sock_put(sk);

}



/**
@@ -596,9 +601,12 @@ void can_rx_unregister(struct net_device *dev, canid_t can_id, canid_t mask, 
	spin_unlock(&can_rcvlists_lock);



	/* schedule the receiver item for deletion */

	if (r)

	if (r) {

		if (r->sk)

			sock_hold(r->sk);

		call_rcu(&r->rcu, can_rx_delete_receiver);

	}

}

EXPORT_SYMBOL(can_rx_unregister);



static inline void deliver(struct sk_buff *skb, struct receiver *r)

net/can/af_can.h

+2 −1
Original line number Diff line number Diff line
@@ -50,13 +50,14 @@ 


struct receiver {

	struct hlist_node list;

	struct rcu_head rcu;

	canid_t can_id;

	canid_t mask;

	unsigned long matches;

	void (*func)(struct sk_buff *, void *);

	void *data;

	char *ident;

	struct sock *sk;

	struct rcu_head rcu;

};



#define CAN_SFF_RCV_ARRAY_SZ (1 << CAN_SFF_ID_BITS)

net/can/bcm.c

+2 −2
Original line number Diff line number Diff line
@@ -1216,7 +1216,7 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg, 
				err = can_rx_register(dev, op->can_id,

						      REGMASK(op->can_id),

						      bcm_rx_handler, op,

						      "bcm");

						      "bcm", sk);



				op->rx_reg_dev = dev;

				dev_put(dev);
@@ -1225,7 +1225,7 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg, 
		} else

			err = can_rx_register(NULL, op->can_id,

					      REGMASK(op->can_id),

					      bcm_rx_handler, op, "bcm");

					      bcm_rx_handler, op, "bcm", sk);

		if (err) {

			/* this bcm rx op is broken -> remove it */

			list_del(&op->list);

net/can/gw.c

+1 −1
Original line number Diff line number Diff line
@@ -442,7 +442,7 @@ static inline int cgw_register_filter(struct cgw_job *gwj) 
{

	return can_rx_register(gwj->src.dev, gwj->ccgw.filter.can_id,

			       gwj->ccgw.filter.can_mask, can_can_gw_rcv,

			       gwj, "gw");

			       gwj, "gw", NULL);

}



static inline void cgw_unregister_filter(struct cgw_job *gwj)