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: Zhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/can/core.h b/include/linux/can/core.h
index a0875001b13c84ad70a9b2909654e9ffb6824c58..df08a41d5be5f26cfa4cdc74935f5eae7fa51385 100644 (file)
--- a/include/linux/can/core.h
+++ b/include/linux/can/core.h
@@ -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,
-                           void (*func)(struct sk_buff *, void *),
-                           void *data, char *ident);
+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, struct sock *sk);
 
 extern void can_rx_unregister(struct net_device *dev, canid_t can_id,
                              canid_t mask,

diff --git a/net/can/af_can.c b/net/can/af_can.c
index 1108079d934f8383a599d7997b08100fca0465e9..5488e4a6ccd062e6f6e7e2b841dde5ef055d4337 100644 (file)
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -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);
 }
 
 /**
@@ -596,8 +601,11 @@ 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);
 

diff --git a/net/can/af_can.h b/net/can/af_can.h
index fca0fe9fc45a497cdf3da82d5414e846e7cc61b7..b86f5129e8385fe84ef671bb914e8e05c2977ca0 100644 (file)
--- a/net/can/af_can.h
+++ b/net/can/af_can.h
@@ -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)

diff --git a/net/can/bcm.c b/net/can/bcm.c
index 21ac75390e3d64f795faad074b515d34ce0bbfa3..5c94071819188a2b92db9ae7fe1e0d41fb9a27c6 100644 (file)
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -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);

diff --git a/net/can/gw.c b/net/can/gw.c
index a54ab0c821048ab2034bf32cef3c1f35e0dc82a5..7056a1a2bb70098e691ce557f05e5bc1f27cb42f 100644 (file)
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -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)

diff --git a/net/can/raw.c b/net/can/raw.c
index b075f028d7e23958e9433a4b19f4475ad930b547..6dc546a06673ff41fc121c546ebd0567bb0da05f 100644 (file)
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -190,7 +190,7 @@ static int raw_enable_filters(struct net_device *dev, struct sock *sk,
        for (i = 0; i < count; i++) {
                err = can_rx_register(dev, filter[i].can_id,
                                      filter[i].can_mask,
-                                     raw_rcv, sk, "raw");
+                                     raw_rcv, sk, "raw", sk);
                if (err) {
                        /* clean up successfully registered filters */
                        while (--i >= 0)
@@ -211,7 +211,7 @@ static int raw_enable_errfilter(struct net_device *dev, struct sock *sk,
 
        if (err_mask)
                err = can_rx_register(dev, 0, err_mask | CAN_ERR_FLAG,
-                                     raw_rcv, sk, "raw");
+                                     raw_rcv, sk, "raw", sk);
 
        return err;
 }