[PATCH net v1 0/2] tipc: topology server fixes

[PATCH net v1 0/2] tipc: topology server fixes

[Parthasarathy Bhuvaragan]

The following commits fixes two race conditions causing general
protection faults.

Parthasarathy Bhuvaragan (1):
  tipc: remove subscription references only for pending timers

Ying Xue (1):
  tipc: fix a race condition of releasing subscriber object

 net/tipc/subscr.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

-- 
2.1.4


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[PATCH net v1 1/2] tipc: remove subscription references only for pending timers

[Parthasarathy Bhuvaragan]

In commit, 139bb36f754a ("tipc: advance the time of deleting
subscription from subscriber->subscrp_list"), we delete the
subscription from the subscribers list and from nametable
unconditionally. This leads to the following bug if the timer
running tipc_subscrp_timeout() in another CPU accesses the
subscription list after the subscription delete request.

[39.570] general protection fault: 0000 [#1] SMP
::
[39.574] task: ffffffff81c10540 task.stack: ffffffff81c00000
[39.575] RIP: 0010:tipc_subscrp_timeout+0x32/0x80 [tipc]
[39.576] RSP: 0018:ffff88003ba03e90 EFLAGS: 00010282
[39.576] RAX: dead000000000200 RBX: ffff88003f0f3600 RCX: 0000000000000101
[39.577] RDX: dead000000000100 RSI: 0000000000000201 RDI: ffff88003f0d7948
[39.578] RBP: ffff88003ba03ea0 R08: 0000000000000001 R09: ffff88003ba03ef8
[39.579] R10: 000000000000014f R11: 0000000000000000 R12: ffff88003f0d7948
[39.580] R13: ffff88003f0f3618 R14: ffffffffa006c250 R15: ffff88003f0f3600
[39.581] FS:  0000000000000000(0000) GS:ffff88003ba00000(0000) knlGS:0000000000000000
[39.582] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[39.583] CR2: 00007f831c6e0714 CR3: 000000003d3b0000 CR4: 00000000000006f0
[39.584] Call Trace:
[39.584]  <IRQ>
[39.585]  call_timer_fn+0x3d/0x180
[39.585]  ? tipc_subscrb_rcv_cb+0x260/0x260 [tipc]
[39.586]  run_timer_softirq+0x168/0x1f0
[39.586]  ? sched_clock_cpu+0x16/0xc0
[39.587]  __do_softirq+0x9b/0x2de
[39.587]  irq_exit+0x60/0x70
[39.588]  smp_apic_timer_interrupt+0x3d/0x50
[39.588]  apic_timer_interrupt+0x86/0x90
[39.589] RIP: 0010:default_idle+0x20/0xf0
[39.589] RSP: 0018:ffffffff81c03e58 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
[39.590] RAX: 0000000000000000 RBX: ffffffff81c10540 RCX: 0000000000000000
[39.591] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[39.592] RBP: ffffffff81c03e68 R08: 0000000000000000 R09: 0000000000000000
[39.593] R10: ffffc90001cbbe00 R11: 0000000000000000 R12: 0000000000000000
[39.594] R13: ffffffff81c10540 R14: 0000000000000000 R15: 0000000000000000
[39.595]  </IRQ>
::
[39.603] RIP: tipc_subscrp_timeout+0x32/0x80 [tipc] RSP: ffff88003ba03e90
[39.604] ---[ end trace 79ce94b7216cb459 ]---

Fixes: 139bb36f754a ("tipc: advance the time of deleting subscription from subscriber->subscrp_list")
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
---
 net/tipc/subscr.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/net/tipc/subscr.c b/net/tipc/subscr.c
index 0bf91cd3733c..f2c81f42dfda 100644
--- a/net/tipc/subscr.c
+++ b/net/tipc/subscr.c
@@ -52,7 +52,6 @@ struct tipc_subscriber {
 	struct list_head subscrp_list;
 };
 
-static void tipc_subscrp_delete(struct tipc_subscription *sub);
 static void tipc_subscrb_put(struct tipc_subscriber *subscriber);
 
 /**
@@ -197,15 +196,19 @@ static void tipc_subscrb_subscrp_delete(struct tipc_subscriber *subscriber,
 {
 	struct list_head *subscription_list = &subscriber->subscrp_list;
 	struct tipc_subscription *sub, *temp;
+	u32 timeout;
 
 	spin_lock_bh(&subscriber->lock);
 	list_for_each_entry_safe(sub, temp, subscription_list,  subscrp_list) {
 		if (s && memcmp(s, &sub->evt.s, sizeof(struct tipc_subscr)))
 			continue;
 
-		tipc_nametbl_unsubscribe(sub);
-		list_del(&sub->subscrp_list);
-		tipc_subscrp_delete(sub);
+		timeout = htohl(sub->evt.s.timeout, sub->swap);
+		if (timeout == TIPC_WAIT_FOREVER || del_timer(&sub->timer)) {
+			tipc_nametbl_unsubscribe(sub);
+			list_del(&sub->subscrp_list);
+			tipc_subscrp_put(sub);
+		}
 
 		if (s)
 			break;
@@ -236,14 +239,6 @@ static void tipc_subscrb_delete(struct tipc_subscriber *subscriber)
 	tipc_subscrb_put(subscriber);
 }
 
-static void tipc_subscrp_delete(struct tipc_subscription *sub)
-{
-	u32 timeout = htohl(sub->evt.s.timeout, sub->swap);
-
-	if (timeout == TIPC_WAIT_FOREVER || del_timer(&sub->timer))
-		tipc_subscrp_put(sub);
-}
-
 static void tipc_subscrp_cancel(struct tipc_subscr *s,
 				struct tipc_subscriber *subscriber)
 {
-- 
2.1.4


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[PATCH net v1 2/2] tipc: fix a race condition of releasing subscriber object

[Parthasarathy Bhuvaragan]

From: Ying Xue <ying.xue@windriver.com>

No matter whether a request is inserted into workqueue as a work item
to cancel a subscription or to delete a subscription's subscriber
asynchronously, the work items may be executed in different workers.
As a result, it doesn't mean that one request which is raised prior to
another request is definitely handled before the latter. By contrast,
if the latter request is executed before the former request, below
error may happen:

[  656.183644] BUG: spinlock bad magic on CPU#0, kworker/u8:0/12117
[  656.184487] general protection fault: 0000 [#1] SMP
[  656.185160] Modules linked in: tipc ip6_udp_tunnel udp_tunnel 9pnet_virtio 9p 9pnet virtio_net virtio_pci virtio_ring virtio [last unloaded: ip6_udp_tunnel]
[  656.187003] CPU: 0 PID: 12117 Comm: kworker/u8:0 Not tainted 4.11.0-rc7+ #6
[  656.187920] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  656.188690] Workqueue: tipc_rcv tipc_recv_work [tipc]
[  656.189371] task: ffff88003f5cec40 task.stack: ffffc90004448000
[  656.190157] RIP: 0010:spin_bug+0xdd/0xf0
[  656.190678] RSP: 0018:ffffc9000444bcb8 EFLAGS: 00010202
[  656.191375] RAX: 0000000000000034 RBX: ffff88003f8d1388 RCX: 0000000000000000
[  656.192321] RDX: ffff88003ba13708 RSI: ffff88003ba0cd08 RDI: ffff88003ba0cd08
[  656.193265] RBP: ffffc9000444bcd0 R08: 0000000000000030 R09: 000000006b6b6b6b
[  656.194208] R10: ffff8800bde3e000 R11: 00000000000001b4 R12: 6b6b6b6b6b6b6b6b
[  656.195157] R13: ffffffff81a3ca64 R14: ffff88003f8d1388 R15: ffff88003f8d13a0
[  656.196101] FS:  0000000000000000(0000) GS:ffff88003ba00000(0000) knlGS:0000000000000000
[  656.197172] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  656.197935] CR2: 00007f0b3d2e6000 CR3: 000000003ef9e000 CR4: 00000000000006f0
[  656.198873] Call Trace:
[  656.199210]  do_raw_spin_lock+0x66/0xa0
[  656.199735]  _raw_spin_lock_bh+0x19/0x20
[  656.200258]  tipc_subscrb_subscrp_delete+0x28/0xf0 [tipc]
[  656.200990]  tipc_subscrb_rcv_cb+0x45/0x260 [tipc]
[  656.201632]  tipc_receive_from_sock+0xaf/0x100 [tipc]
[  656.202299]  tipc_recv_work+0x2b/0x60 [tipc]
[  656.202872]  process_one_work+0x157/0x420
[  656.203404]  worker_thread+0x69/0x4c0
[  656.203898]  kthread+0x138/0x170
[  656.204328]  ? process_one_work+0x420/0x420
[  656.204889]  ? kthread_create_on_node+0x40/0x40
[  656.205527]  ret_from_fork+0x29/0x40
[  656.206012] Code: 48 8b 0c 25 00 c5 00 00 48 c7 c7 f0 24 a3 81 48 81 c1 f0 05 00 00 65 8b 15 61 ef f5 7e e8 9a 4c 09 00 4d 85 e4 44 8b 4b 08 74 92 <45> 8b 84 24 40 04 00 00 49 8d 8c 24 f0 05 00 00 eb 8d 90 0f 1f
[  656.208504] RIP: spin_bug+0xdd/0xf0 RSP: ffffc9000444bcb8
[  656.209798] ---[ end trace e2a800e6eb0770be ]---

In above scenario, the request of deleting subscriber was performed
earlier than the request of canceling a subscription although the
latter was issued before the former, which means tipc_subscrb_delete()
was called before tipc_subscrp_cancel(). As a result, when
tipc_subscrb_subscrp_delete() called by tipc_subscrp_cancel() was
executed to cancel a subscription, the subscription's subscriber
refcnt had been decreased to 1. After tipc_subscrp_delete() where
the subscriber was freed because its refcnt was decremented to zero,
but the subscriber's lock had to be released, as a consequence, panic
happened.

By contrast, if we increase subscriber's refcnt before
tipc_subscrb_subscrp_delete() is called in tipc_subscrp_cancel(),
the panic issue can be avoided.

Fixes: d094c4d5f5c7 ("tipc: add subscription refcount to avoid invalid delete")
Reported-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: Ying Xue <ying.xue@windriver.com>
---
 net/tipc/subscr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/tipc/subscr.c b/net/tipc/subscr.c
index f2c81f42dfda..be3d9e3183dc 100644
--- a/net/tipc/subscr.c
+++ b/net/tipc/subscr.c
@@ -242,7 +242,9 @@ static void tipc_subscrb_delete(struct tipc_subscriber *subscriber)
 static void tipc_subscrp_cancel(struct tipc_subscr *s,
 				struct tipc_subscriber *subscriber)
 {
+	tipc_subscrb_get(subscriber);
 	tipc_subscrb_subscrp_delete(subscriber, s);
+	tipc_subscrb_put(subscriber);
 }
 
 static struct tipc_subscription *tipc_subscrp_create(struct net *net,
-- 
2.1.4


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Re: [PATCH net v1 0/2] tipc: topology server fixes

[David Miller]

From: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Date: Tue, 22 Aug 2017 12:28:39 +0200

> The following commits fixes two race conditions causing general
> protection faults.

Series applied, thank you.