can: Fix kernel panic at security_sock_rcv_skb

commit f1712c73714088a7252d276a57126d56c7d37e64 upstream.

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>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/include/linux/can/core.h b/include/linux/can/core.h
index 78c6c52073ad62948a7d750951ed94d232957048..6bdc00b6df01d192cd0f990c870c97268fe819dc 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 d3668c55b088bc940e1848c4b551cdb6e2626448..34064aa88f02a2cc0ff68315cffb4fd20d53d824 100644 (file)
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -425,6 +425,7 @@ 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 indentification
+ * @sk: socket pointer (might be NULL)
  *
  * Description:
  *  Invokes the callback function with the received sk_buff and the given
@@ -448,7 +449,7 @@ 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;
@@ -476,6 +477,7 @@ 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++;
@@ -500,8 +502,11 @@ 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);
 }
 
 /**
@@ -576,8 +581,11 @@ 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 1dccb4c33894af7074ee85e320e32c035dbfa368..0e95be42358712c3bf679e0b0db4e93806e3a26e 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;
 };
 
 enum { RX_ERR, RX_ALL, RX_FIL, RX_INV, RX_EFF, RX_MAX };

diff --git a/net/can/bcm.c b/net/can/bcm.c
index dd0781c49ebb4a9d709f04b5854dfb001d8f379e..725ce812cfbc30672a32afa8621f0f55e55d6b7f 100644 (file)
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1169,7 +1169,7 @@ 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);
@@ -1178,7 +1178,7 @@ 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 de25455b4e3e827bfae94b8a835a69c3191fe569..2ad8aa4f9f0ba55e2b0b01a7334bf81a85f32c63 100644 (file)
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -435,7 +435,7 @@ 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 1085e65f848eab9a3a634ad16b37d70bd80830b5..f4d86485571fdc0e4d1ddcbea66f505d2663b0c6 100644 (file)
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -168,7 +168,7 @@ 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)
@@ -189,7 +189,7 @@ 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;
 }