ax25: netrom: rose: Fix timer oopses

Wrong ax25_cb refcounting in ax25_send_frame() and by its callers can
cause timer oopses (first reported with 2.6.29.6 kernel).

Fixes: http://bugzilla.kernel.org/show_bug.cgi?id=14905

Reported-by: Bernard Pidoux <bpidoux@free.fr>
Tested-by: Bernard Pidoux <bpidoux@free.fr>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 25 insertions, 5 deletions

diff --git a/net/ax25/ax25_out.c b/net/ax25/ax25_out.c
index bf706f83a5c9..14912600ec57 100644
--- a/net/ax25/ax25_out.c
+++ b/net/ax25/ax25_out.c
@@ -92,6 +92,12 @@ ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, ax25_address *src, ax2
 #endif
         }
 
+        /*
+         * There is one ref for the state machine; a caller needs
+         * one more to put it back, just like with the existing one.
+         */
+        ax25_cb_hold(ax25);
+
         ax25_cb_add(ax25);
 
         ax25->state = AX25_STATE_1;
diff --git a/net/netrom/nr_route.c b/net/netrom/nr_route.c
index aacba76070fc..e2e2d33cafdf 100644
--- a/net/netrom/nr_route.c
+++ b/net/netrom/nr_route.c
@@ -843,12 +843,13 @@ int nr_route_frame(struct sk_buff *skb, ax25_cb *ax25)
         dptr  = skb_push(skb, 1);
         *dptr = AX25_P_NETROM;
 
-        ax25s = ax25_send_frame(skb, 256, (ax25_address *)dev->dev_addr, &nr_neigh->callsign, nr_neigh->digipeat, nr_neigh->dev);
-        if (nr_neigh->ax25 && ax25s) {
-                /* We were already holding this ax25_cb */
+        ax25s = nr_neigh->ax25;
+        nr_neigh->ax25 = ax25_send_frame(skb, 256,
+                                         (ax25_address *)dev->dev_addr,
+                                         &nr_neigh->callsign,
+                                         nr_neigh->digipeat, nr_neigh->dev);
+        if (ax25s)
                 ax25_cb_put(ax25s);
-        }
-        nr_neigh->ax25 = ax25s;
 
         dev_put(dev);
         ret = (nr_neigh->ax25 != NULL);
diff --git a/net/rose/rose_link.c b/net/rose/rose_link.c
index bd86a63960ce..5ef5f6988a2e 100644
--- a/net/rose/rose_link.c
+++ b/net/rose/rose_link.c
@@ -101,13 +101,17 @@ static void rose_t0timer_expiry(unsigned long param)
 static int rose_send_frame(struct sk_buff *skb, struct rose_neigh *neigh)
 {
         ax25_address *rose_call;
+        ax25_cb *ax25s;
 
         if (ax25cmp(&rose_callsign, &null_ax25_address) == 0)
                 rose_call = (ax25_address *)neigh->dev->dev_addr;
         else
                 rose_call = &rose_callsign;
 
+        ax25s = neigh->ax25;
         neigh->ax25 = ax25_send_frame(skb, 260, rose_call, &neigh->callsign, neigh->digipeat, neigh->dev);
+        if (ax25s)
+                ax25_cb_put(ax25s);
 
         return (neigh->ax25 != NULL);
 }
@@ -120,13 +124,17 @@ static int rose_send_frame(struct sk_buff *skb, struct rose_neigh *neigh)
 static int rose_link_up(struct rose_neigh *neigh)
 {
         ax25_address *rose_call;
+        ax25_cb *ax25s;
 
         if (ax25cmp(&rose_callsign, &null_ax25_address) == 0)
                 rose_call = (ax25_address *)neigh->dev->dev_addr;
         else
                 rose_call = &rose_callsign;
 
+        ax25s = neigh->ax25;
         neigh->ax25 = ax25_find_cb(rose_call, &neigh->callsign, neigh->digipeat, neigh->dev);
+        if (ax25s)
+                ax25_cb_put(ax25s);
 
         return (neigh->ax25 != NULL);
 }
diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c
index 795c4b025e31..70a0b3b4b4d2 100644
--- a/net/rose/rose_route.c
+++ b/net/rose/rose_route.c
@@ -235,6 +235,8 @@ static void rose_remove_neigh(struct rose_neigh *rose_neigh)
 
         if ((s = rose_neigh_list) == rose_neigh) {
                 rose_neigh_list = rose_neigh->next;
+                if (rose_neigh->ax25)
+                        ax25_cb_put(rose_neigh->ax25);
                 kfree(rose_neigh->digipeat);
                 kfree(rose_neigh);
                 return;
@@ -243,6 +245,8 @@ static void rose_remove_neigh(struct rose_neigh *rose_neigh)
         while (s != NULL && s->next != NULL) {
                 if (s->next == rose_neigh) {
                         s->next = rose_neigh->next;
+                        if (rose_neigh->ax25)
+                                ax25_cb_put(rose_neigh->ax25);
                         kfree(rose_neigh->digipeat);
                         kfree(rose_neigh);
                         return;
@@ -812,6 +816,7 @@ void rose_link_failed(ax25_cb *ax25, int reason)
 
         if (rose_neigh != NULL) {
                 rose_neigh->ax25 = NULL;
+                ax25_cb_put(ax25);
 
                 rose_del_route_by_neigh(rose_neigh);
                 rose_kill_by_neigh(rose_neigh);