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/net/can/af_can.c b/net/can/af_can.c
index 1108079..5488e4a 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -445,6 +445,7 @@
* @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 @@
*/
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 @@
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 @@
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 @@
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 fca0fe9..b86f512 100644
--- 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 21ac753..5c94071 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1216,7 +1216,7 @@
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 @@
} 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 a54ab0c..7056a1a 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -442,7 +442,7 @@
{
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 b075f02..6dc546a 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -190,7 +190,7 @@
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 @@
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;
}