* [PATCH net] cls_u32: fix use after free in u32_destroy_key()
@ 2018-02-02 13:20 Paolo Abeni
2018-02-02 13:35 ` Paolo Abeni
2018-02-02 14:30 ` [PATCH net v2] " Paolo Abeni
0 siblings, 2 replies; 7+ messages in thread
From: Paolo Abeni @ 2018-02-02 13:20 UTC (permalink / raw)
To: netdev; +Cc: David S. Miller, Jamal Hadi Salim, Cong Wang, Jiri Pirko
Li Shuang reported an Oops with cls_u32 due to an use-after-free
in u32_destroy_key(). The use-after-free can be triggered with:
dev=lo
tc qdisc add dev $dev root handle 1: htb default 10
tc filter add dev $dev parent 1: prio 5 handle 1: protocol ip u32 divisor 256
tc filter add dev $dev protocol ip parent 1: prio 5 u32 ht 800:: match ip dst\
10.0.0.0/8 hashkey mask 0x0000ff00 at 16 link 1:
tc qdisc del dev $dev root
Which causes the following kasan splat:
==================================================================
BUG: KASAN: use-after-free in u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
Read of size 4 at addr ffff881b83dae618 by task kworker/u48:5/571
CPU: 17 PID: 571 Comm: kworker/u48:5 Not tainted 4.15.0+ #87
Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.1.7 06/16/2016
Workqueue: tc_filter_workqueue u32_delete_key_freepf_work [cls_u32]
Call Trace:
dump_stack+0xd6/0x182
? dma_virt_map_sg+0x22e/0x22e
print_address_description+0x73/0x290
kasan_report+0x277/0x360
? u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
u32_delete_key_freepf_work+0x1c/0x30 [cls_u32]
process_one_work+0xae0/0x1c80
? sched_clock+0x5/0x10
? pwq_dec_nr_in_flight+0x3c0/0x3c0
? _raw_spin_unlock_irq+0x29/0x40
? trace_hardirqs_on_caller+0x381/0x570
? _raw_spin_unlock_irq+0x29/0x40
? finish_task_switch+0x1e5/0x760
? finish_task_switch+0x208/0x760
? preempt_notifier_dec+0x20/0x20
? __schedule+0x839/0x1ee0
? check_noncircular+0x20/0x20
? firmware_map_remove+0x73/0x73
? find_held_lock+0x39/0x1c0
? worker_thread+0x434/0x1820
? lock_contended+0xee0/0xee0
? lock_release+0x1100/0x1100
? init_rescuer.part.16+0x150/0x150
? retint_kernel+0x10/0x10
worker_thread+0x216/0x1820
? process_one_work+0x1c80/0x1c80
? lock_acquire+0x1a5/0x540
? lock_downgrade+0x6b0/0x6b0
? sched_clock+0x5/0x10
? lock_release+0x1100/0x1100
? compat_start_thread+0x80/0x80
? do_raw_spin_trylock+0x190/0x190
? _raw_spin_unlock_irq+0x29/0x40
? trace_hardirqs_on_caller+0x381/0x570
? _raw_spin_unlock_irq+0x29/0x40
? finish_task_switch+0x1e5/0x760
? finish_task_switch+0x208/0x760
? preempt_notifier_dec+0x20/0x20
? __schedule+0x839/0x1ee0
? kmem_cache_alloc_trace+0x143/0x320
? firmware_map_remove+0x73/0x73
? sched_clock+0x5/0x10
? sched_clock_cpu+0x18/0x170
? find_held_lock+0x39/0x1c0
? schedule+0xf3/0x3b0
? lock_downgrade+0x6b0/0x6b0
? __schedule+0x1ee0/0x1ee0
? do_wait_intr_irq+0x340/0x340
? do_raw_spin_trylock+0x190/0x190
? _raw_spin_unlock_irqrestore+0x32/0x60
? process_one_work+0x1c80/0x1c80
? process_one_work+0x1c80/0x1c80
kthread+0x312/0x3d0
? kthread_create_worker_on_cpu+0xc0/0xc0
ret_from_fork+0x3a/0x50
Allocated by task 1688:
kasan_kmalloc+0xa0/0xd0
__kmalloc+0x162/0x380
u32_change+0x1220/0x3c9e [cls_u32]
tc_ctl_tfilter+0x1ba6/0x2f80
rtnetlink_rcv_msg+0x4f0/0x9d0
netlink_rcv_skb+0x124/0x320
netlink_unicast+0x430/0x600
netlink_sendmsg+0x8fa/0xd60
sock_sendmsg+0xb1/0xe0
___sys_sendmsg+0x678/0x980
__sys_sendmsg+0xc4/0x210
do_syscall_64+0x232/0x7f0
return_from_SYSCALL_64+0x0/0x75
Freed by task 112:
kasan_slab_free+0x71/0xc0
kfree+0x114/0x320
rcu_process_callbacks+0xc3f/0x1600
__do_softirq+0x2bf/0xc06
The buggy address belongs to the object at ffff881b83dae600
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 24 bytes inside of
4096-byte region [ffff881b83dae600, ffff881b83daf600)
The buggy address belongs to the page:
page:ffffea006e0f6a00 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0
flags: 0x17ffffc0008100(slab|head)
raw: 0017ffffc0008100 0000000000000000 0000000000000000 0000000100070007
raw: dead000000000100 dead000000000200 ffff880187c0e600 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff881b83dae500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff881b83dae580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff881b83dae600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff881b83dae680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff881b83dae700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
The problem is that the htnode is freed before the linked knodes and the
latter will try to access the first at u32_destroy_key() time.
This change addresses the issue using the htnode refcnt to guarantee
the correct free order. While at it also add a pedantic and possibly
unneeded RCU annotation, to keep sparse happy.
Reported-by: Li Shuang <shuali@redhat.com>
Fixes: c0d378ef1266 ("net_sched: use tcf_queue_work() in u32 filter")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
net/sched/cls_u32.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 60c892c36a60..0e3fbcf343e2 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -398,10 +398,16 @@ static int u32_init(struct tcf_proto *tp)
static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n,
bool free_pf)
{
+ struct tc_u_hnode *ht;
+
tcf_exts_destroy(&n->exts);
tcf_exts_put_net(&n->exts);
- if (n->ht_down)
- n->ht_down->refcnt--;
+
+ rcu_read_lock_bh();
+ ht = rcu_dereference_bh(n->ht_down);
+ if (ht && ht->refcnt-- == 0)
+ kfree(ht);
+ rcu_read_unlock_bh();
#ifdef CONFIG_CLS_U32_PERF
if (free_pf)
free_percpu(n->pf);
@@ -624,7 +630,12 @@ static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
idr_destroy(&ht->handle_idr);
idr_remove_ext(&tp_c->handle_idr, ht->handle);
RCU_INIT_POINTER(*hn, ht->next);
- kfree_rcu(ht, rcu);
+
+ /* u32_destroy_key() will will later free ht for us, if
+ * it's still referenced by some knode
+ */
+ if (ht->refcnt == 0)
+ kfree_rcu(ht, rcu);
return 0;
}
}
@@ -667,7 +678,11 @@ static void u32_destroy(struct tcf_proto *tp, struct netlink_ext_ack *extack)
while ((ht = rtnl_dereference(tp_c->hlist)) != NULL) {
RCU_INIT_POINTER(tp_c->hlist, ht->next);
- kfree_rcu(ht, rcu);
+ /* u32_destroy_key() will will later free ht for us, if
+ * it's still referenced by some knode
+ */
+ if (ht->refcnt == 0)
+ kfree_rcu(ht, rcu);
}
idr_destroy(&tp_c->handle_idr);
--
2.14.3
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH net] cls_u32: fix use after free in u32_destroy_key()
2018-02-02 13:20 [PATCH net] cls_u32: fix use after free in u32_destroy_key() Paolo Abeni
@ 2018-02-02 13:35 ` Paolo Abeni
2018-02-02 14:30 ` [PATCH net v2] " Paolo Abeni
1 sibling, 0 replies; 7+ messages in thread
From: Paolo Abeni @ 2018-02-02 13:35 UTC (permalink / raw)
To: netdev; +Cc: David S. Miller, Jamal Hadi Salim, Cong Wang, Jiri Pirko
On Fri, 2018-02-02 at 14:20 +0100, Paolo Abeni wrote:
> Li Shuang reported an Oops with cls_u32 due to an use-after-free
> in u32_destroy_key(). The use-after-free can be triggered with:
>
> dev=lo
> tc qdisc add dev $dev root handle 1: htb default 10
> tc filter add dev $dev parent 1: prio 5 handle 1: protocol ip u32 divisor 256
> tc filter add dev $dev protocol ip parent 1: prio 5 u32 ht 800:: match ip dst\
> 10.0.0.0/8 hashkey mask 0x0000ff00 at 16 link 1:
> tc qdisc del dev $dev root
>
> Which causes the following kasan splat:
>
> ==================================================================
> BUG: KASAN: use-after-free in u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
> Read of size 4 at addr ffff881b83dae618 by task kworker/u48:5/571
>
> CPU: 17 PID: 571 Comm: kworker/u48:5 Not tainted 4.15.0+ #87
> Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.1.7 06/16/2016
> Workqueue: tc_filter_workqueue u32_delete_key_freepf_work [cls_u32]
> Call Trace:
> dump_stack+0xd6/0x182
> ? dma_virt_map_sg+0x22e/0x22e
> print_address_description+0x73/0x290
> kasan_report+0x277/0x360
> ? u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
> u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
> u32_delete_key_freepf_work+0x1c/0x30 [cls_u32]
> process_one_work+0xae0/0x1c80
> ? sched_clock+0x5/0x10
> ? pwq_dec_nr_in_flight+0x3c0/0x3c0
> ? _raw_spin_unlock_irq+0x29/0x40
> ? trace_hardirqs_on_caller+0x381/0x570
> ? _raw_spin_unlock_irq+0x29/0x40
> ? finish_task_switch+0x1e5/0x760
> ? finish_task_switch+0x208/0x760
> ? preempt_notifier_dec+0x20/0x20
> ? __schedule+0x839/0x1ee0
> ? check_noncircular+0x20/0x20
> ? firmware_map_remove+0x73/0x73
> ? find_held_lock+0x39/0x1c0
> ? worker_thread+0x434/0x1820
> ? lock_contended+0xee0/0xee0
> ? lock_release+0x1100/0x1100
> ? init_rescuer.part.16+0x150/0x150
> ? retint_kernel+0x10/0x10
> worker_thread+0x216/0x1820
> ? process_one_work+0x1c80/0x1c80
> ? lock_acquire+0x1a5/0x540
> ? lock_downgrade+0x6b0/0x6b0
> ? sched_clock+0x5/0x10
> ? lock_release+0x1100/0x1100
> ? compat_start_thread+0x80/0x80
> ? do_raw_spin_trylock+0x190/0x190
> ? _raw_spin_unlock_irq+0x29/0x40
> ? trace_hardirqs_on_caller+0x381/0x570
> ? _raw_spin_unlock_irq+0x29/0x40
> ? finish_task_switch+0x1e5/0x760
> ? finish_task_switch+0x208/0x760
> ? preempt_notifier_dec+0x20/0x20
> ? __schedule+0x839/0x1ee0
> ? kmem_cache_alloc_trace+0x143/0x320
> ? firmware_map_remove+0x73/0x73
> ? sched_clock+0x5/0x10
> ? sched_clock_cpu+0x18/0x170
> ? find_held_lock+0x39/0x1c0
> ? schedule+0xf3/0x3b0
> ? lock_downgrade+0x6b0/0x6b0
> ? __schedule+0x1ee0/0x1ee0
> ? do_wait_intr_irq+0x340/0x340
> ? do_raw_spin_trylock+0x190/0x190
> ? _raw_spin_unlock_irqrestore+0x32/0x60
> ? process_one_work+0x1c80/0x1c80
> ? process_one_work+0x1c80/0x1c80
> kthread+0x312/0x3d0
> ? kthread_create_worker_on_cpu+0xc0/0xc0
> ret_from_fork+0x3a/0x50
>
> Allocated by task 1688:
> kasan_kmalloc+0xa0/0xd0
> __kmalloc+0x162/0x380
> u32_change+0x1220/0x3c9e [cls_u32]
> tc_ctl_tfilter+0x1ba6/0x2f80
> rtnetlink_rcv_msg+0x4f0/0x9d0
> netlink_rcv_skb+0x124/0x320
> netlink_unicast+0x430/0x600
> netlink_sendmsg+0x8fa/0xd60
> sock_sendmsg+0xb1/0xe0
> ___sys_sendmsg+0x678/0x980
> __sys_sendmsg+0xc4/0x210
> do_syscall_64+0x232/0x7f0
> return_from_SYSCALL_64+0x0/0x75
>
> Freed by task 112:
> kasan_slab_free+0x71/0xc0
> kfree+0x114/0x320
> rcu_process_callbacks+0xc3f/0x1600
> __do_softirq+0x2bf/0xc06
>
> The buggy address belongs to the object at ffff881b83dae600
> which belongs to the cache kmalloc-4096 of size 4096
> The buggy address is located 24 bytes inside of
> 4096-byte region [ffff881b83dae600, ffff881b83daf600)
> The buggy address belongs to the page:
> page:ffffea006e0f6a00 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0
> flags: 0x17ffffc0008100(slab|head)
> raw: 0017ffffc0008100 0000000000000000 0000000000000000 0000000100070007
> raw: dead000000000100 dead000000000200 ffff880187c0e600 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff881b83dae500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff881b83dae580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >ffff881b83dae600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff881b83dae680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff881b83dae700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
> The problem is that the htnode is freed before the linked knodes and the
> latter will try to access the first at u32_destroy_key() time.
> This change addresses the issue using the htnode refcnt to guarantee
> the correct free order. While at it also add a pedantic and possibly
> unneeded RCU annotation, to keep sparse happy.
>
> Reported-by: Li Shuang <shuali@redhat.com>
> Fixes: c0d378ef1266 ("net_sched: use tcf_queue_work() in u32 filter")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> net/sched/cls_u32.c | 23 +++++++++++++++++++----
> 1 file changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
> index 60c892c36a60..0e3fbcf343e2 100644
> --- a/net/sched/cls_u32.c
> +++ b/net/sched/cls_u32.c
> @@ -398,10 +398,16 @@ static int u32_init(struct tcf_proto *tp)
> static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n,
> bool free_pf)
> {
> + struct tc_u_hnode *ht;
> +
> tcf_exts_destroy(&n->exts);
> tcf_exts_put_net(&n->exts);
> - if (n->ht_down)
> - n->ht_down->refcnt--;
> +
> + rcu_read_lock_bh();
> + ht = rcu_dereference_bh(n->ht_down);
> + if (ht && ht->refcnt-- == 0)
> + kfree(ht);
> + rcu_read_unlock_bh();
I think I can simply use rtnl_dereference() here. I will double check
and ev. send a v2.
Sorry for the noise,
Paolo
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH net v2] cls_u32: fix use after free in u32_destroy_key()
2018-02-02 13:20 [PATCH net] cls_u32: fix use after free in u32_destroy_key() Paolo Abeni
2018-02-02 13:35 ` Paolo Abeni
@ 2018-02-02 14:30 ` Paolo Abeni
2018-02-02 17:54 ` Ivan Vecera
` (2 more replies)
1 sibling, 3 replies; 7+ messages in thread
From: Paolo Abeni @ 2018-02-02 14:30 UTC (permalink / raw)
To: netdev
Cc: David S. Miller, Jamal Hadi Salim, Cong Wang, Jiri Pirko, Li Shuang
Li Shuang reported an Oops with cls_u32 due to an use-after-free
in u32_destroy_key(). The use-after-free can be triggered with:
dev=lo
tc qdisc add dev $dev root handle 1: htb default 10
tc filter add dev $dev parent 1: prio 5 handle 1: protocol ip u32 divisor 256
tc filter add dev $dev protocol ip parent 1: prio 5 u32 ht 800:: match ip dst\
10.0.0.0/8 hashkey mask 0x0000ff00 at 16 link 1:
tc qdisc del dev $dev root
Which causes the following kasan splat:
==================================================================
BUG: KASAN: use-after-free in u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
Read of size 4 at addr ffff881b83dae618 by task kworker/u48:5/571
CPU: 17 PID: 571 Comm: kworker/u48:5 Not tainted 4.15.0+ #87
Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.1.7 06/16/2016
Workqueue: tc_filter_workqueue u32_delete_key_freepf_work [cls_u32]
Call Trace:
dump_stack+0xd6/0x182
? dma_virt_map_sg+0x22e/0x22e
print_address_description+0x73/0x290
kasan_report+0x277/0x360
? u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
u32_delete_key_freepf_work+0x1c/0x30 [cls_u32]
process_one_work+0xae0/0x1c80
? sched_clock+0x5/0x10
? pwq_dec_nr_in_flight+0x3c0/0x3c0
? _raw_spin_unlock_irq+0x29/0x40
? trace_hardirqs_on_caller+0x381/0x570
? _raw_spin_unlock_irq+0x29/0x40
? finish_task_switch+0x1e5/0x760
? finish_task_switch+0x208/0x760
? preempt_notifier_dec+0x20/0x20
? __schedule+0x839/0x1ee0
? check_noncircular+0x20/0x20
? firmware_map_remove+0x73/0x73
? find_held_lock+0x39/0x1c0
? worker_thread+0x434/0x1820
? lock_contended+0xee0/0xee0
? lock_release+0x1100/0x1100
? init_rescuer.part.16+0x150/0x150
? retint_kernel+0x10/0x10
worker_thread+0x216/0x1820
? process_one_work+0x1c80/0x1c80
? lock_acquire+0x1a5/0x540
? lock_downgrade+0x6b0/0x6b0
? sched_clock+0x5/0x10
? lock_release+0x1100/0x1100
? compat_start_thread+0x80/0x80
? do_raw_spin_trylock+0x190/0x190
? _raw_spin_unlock_irq+0x29/0x40
? trace_hardirqs_on_caller+0x381/0x570
? _raw_spin_unlock_irq+0x29/0x40
? finish_task_switch+0x1e5/0x760
? finish_task_switch+0x208/0x760
? preempt_notifier_dec+0x20/0x20
? __schedule+0x839/0x1ee0
? kmem_cache_alloc_trace+0x143/0x320
? firmware_map_remove+0x73/0x73
? sched_clock+0x5/0x10
? sched_clock_cpu+0x18/0x170
? find_held_lock+0x39/0x1c0
? schedule+0xf3/0x3b0
? lock_downgrade+0x6b0/0x6b0
? __schedule+0x1ee0/0x1ee0
? do_wait_intr_irq+0x340/0x340
? do_raw_spin_trylock+0x190/0x190
? _raw_spin_unlock_irqrestore+0x32/0x60
? process_one_work+0x1c80/0x1c80
? process_one_work+0x1c80/0x1c80
kthread+0x312/0x3d0
? kthread_create_worker_on_cpu+0xc0/0xc0
ret_from_fork+0x3a/0x50
Allocated by task 1688:
kasan_kmalloc+0xa0/0xd0
__kmalloc+0x162/0x380
u32_change+0x1220/0x3c9e [cls_u32]
tc_ctl_tfilter+0x1ba6/0x2f80
rtnetlink_rcv_msg+0x4f0/0x9d0
netlink_rcv_skb+0x124/0x320
netlink_unicast+0x430/0x600
netlink_sendmsg+0x8fa/0xd60
sock_sendmsg+0xb1/0xe0
___sys_sendmsg+0x678/0x980
__sys_sendmsg+0xc4/0x210
do_syscall_64+0x232/0x7f0
return_from_SYSCALL_64+0x0/0x75
Freed by task 112:
kasan_slab_free+0x71/0xc0
kfree+0x114/0x320
rcu_process_callbacks+0xc3f/0x1600
__do_softirq+0x2bf/0xc06
The buggy address belongs to the object at ffff881b83dae600
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 24 bytes inside of
4096-byte region [ffff881b83dae600, ffff881b83daf600)
The buggy address belongs to the page:
page:ffffea006e0f6a00 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0
flags: 0x17ffffc0008100(slab|head)
raw: 0017ffffc0008100 0000000000000000 0000000000000000 0000000100070007
raw: dead000000000100 dead000000000200 ffff880187c0e600 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff881b83dae500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff881b83dae580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff881b83dae600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff881b83dae680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff881b83dae700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
The problem is that the htnode is freed before the linked knodes and the
latter will try to access the first at u32_destroy_key() time.
This change addresses the issue using the htnode refcnt to guarantee
the correct free order. While at it also add a RCU annotation,
to keep sparse happy.
v1 -> v2: use rtnl_derefence() instead of RCU read locks
Reported-by: Li Shuang <shuali@redhat.com>
Fixes: c0d378ef1266 ("net_sched: use tcf_queue_work() in u32 filter")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
net/sched/cls_u32.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 60c892c36a60..10440fbf3c68 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -398,10 +398,12 @@ static int u32_init(struct tcf_proto *tp)
static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n,
bool free_pf)
{
+ struct tc_u_hnode *ht = rtnl_dereference(n->ht_down);
+
tcf_exts_destroy(&n->exts);
tcf_exts_put_net(&n->exts);
- if (n->ht_down)
- n->ht_down->refcnt--;
+ if (ht && ht->refcnt-- == 0)
+ kfree(ht);
#ifdef CONFIG_CLS_U32_PERF
if (free_pf)
free_percpu(n->pf);
@@ -624,7 +626,12 @@ static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
idr_destroy(&ht->handle_idr);
idr_remove_ext(&tp_c->handle_idr, ht->handle);
RCU_INIT_POINTER(*hn, ht->next);
- kfree_rcu(ht, rcu);
+
+ /* u32_destroy_key() will will later free ht for us, if
+ * it's still referenced by some knode
+ */
+ if (ht->refcnt == 0)
+ kfree_rcu(ht, rcu);
return 0;
}
}
@@ -667,7 +674,11 @@ static void u32_destroy(struct tcf_proto *tp, struct netlink_ext_ack *extack)
while ((ht = rtnl_dereference(tp_c->hlist)) != NULL) {
RCU_INIT_POINTER(tp_c->hlist, ht->next);
- kfree_rcu(ht, rcu);
+ /* u32_destroy_key() will will later free ht for us, if
+ * it's still referenced by some knode
+ */
+ if (ht->refcnt == 0)
+ kfree_rcu(ht, rcu);
}
idr_destroy(&tp_c->handle_idr);
--
2.14.3
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH net v2] cls_u32: fix use after free in u32_destroy_key()
2018-02-02 14:30 ` [PATCH net v2] " Paolo Abeni
@ 2018-02-02 17:54 ` Ivan Vecera
2018-02-02 21:52 ` Cong Wang
2018-02-03 18:49 ` Paolo Abeni
2 siblings, 0 replies; 7+ messages in thread
From: Ivan Vecera @ 2018-02-02 17:54 UTC (permalink / raw)
To: Paolo Abeni, netdev
Cc: David S. Miller, Jamal Hadi Salim, Cong Wang, Jiri Pirko, Li Shuang
On 2.2.2018 15:30, Paolo Abeni wrote:
> Li Shuang reported an Oops with cls_u32 due to an use-after-free
> in u32_destroy_key(). The use-after-free can be triggered with:
>
> dev=lo
> tc qdisc add dev $dev root handle 1: htb default 10
> tc filter add dev $dev parent 1: prio 5 handle 1: protocol ip u32 divisor 256
> tc filter add dev $dev protocol ip parent 1: prio 5 u32 ht 800:: match ip dst\
> 10.0.0.0/8 hashkey mask 0x0000ff00 at 16 link 1:
> tc qdisc del dev $dev root
>
> Which causes the following kasan splat:
>
> ==================================================================
> BUG: KASAN: use-after-free in u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
> Read of size 4 at addr ffff881b83dae618 by task kworker/u48:5/571
>
> CPU: 17 PID: 571 Comm: kworker/u48:5 Not tainted 4.15.0+ #87
> Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.1.7 06/16/2016
> Workqueue: tc_filter_workqueue u32_delete_key_freepf_work [cls_u32]
> Call Trace:
> dump_stack+0xd6/0x182
> ? dma_virt_map_sg+0x22e/0x22e
> print_address_description+0x73/0x290
> kasan_report+0x277/0x360
> ? u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
> u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
> u32_delete_key_freepf_work+0x1c/0x30 [cls_u32]
> process_one_work+0xae0/0x1c80
> ? sched_clock+0x5/0x10
> ? pwq_dec_nr_in_flight+0x3c0/0x3c0
> ? _raw_spin_unlock_irq+0x29/0x40
> ? trace_hardirqs_on_caller+0x381/0x570
> ? _raw_spin_unlock_irq+0x29/0x40
> ? finish_task_switch+0x1e5/0x760
> ? finish_task_switch+0x208/0x760
> ? preempt_notifier_dec+0x20/0x20
> ? __schedule+0x839/0x1ee0
> ? check_noncircular+0x20/0x20
> ? firmware_map_remove+0x73/0x73
> ? find_held_lock+0x39/0x1c0
> ? worker_thread+0x434/0x1820
> ? lock_contended+0xee0/0xee0
> ? lock_release+0x1100/0x1100
> ? init_rescuer.part.16+0x150/0x150
> ? retint_kernel+0x10/0x10
> worker_thread+0x216/0x1820
> ? process_one_work+0x1c80/0x1c80
> ? lock_acquire+0x1a5/0x540
> ? lock_downgrade+0x6b0/0x6b0
> ? sched_clock+0x5/0x10
> ? lock_release+0x1100/0x1100
> ? compat_start_thread+0x80/0x80
> ? do_raw_spin_trylock+0x190/0x190
> ? _raw_spin_unlock_irq+0x29/0x40
> ? trace_hardirqs_on_caller+0x381/0x570
> ? _raw_spin_unlock_irq+0x29/0x40
> ? finish_task_switch+0x1e5/0x760
> ? finish_task_switch+0x208/0x760
> ? preempt_notifier_dec+0x20/0x20
> ? __schedule+0x839/0x1ee0
> ? kmem_cache_alloc_trace+0x143/0x320
> ? firmware_map_remove+0x73/0x73
> ? sched_clock+0x5/0x10
> ? sched_clock_cpu+0x18/0x170
> ? find_held_lock+0x39/0x1c0
> ? schedule+0xf3/0x3b0
> ? lock_downgrade+0x6b0/0x6b0
> ? __schedule+0x1ee0/0x1ee0
> ? do_wait_intr_irq+0x340/0x340
> ? do_raw_spin_trylock+0x190/0x190
> ? _raw_spin_unlock_irqrestore+0x32/0x60
> ? process_one_work+0x1c80/0x1c80
> ? process_one_work+0x1c80/0x1c80
> kthread+0x312/0x3d0
> ? kthread_create_worker_on_cpu+0xc0/0xc0
> ret_from_fork+0x3a/0x50
>
> Allocated by task 1688:
> kasan_kmalloc+0xa0/0xd0
> __kmalloc+0x162/0x380
> u32_change+0x1220/0x3c9e [cls_u32]
> tc_ctl_tfilter+0x1ba6/0x2f80
> rtnetlink_rcv_msg+0x4f0/0x9d0
> netlink_rcv_skb+0x124/0x320
> netlink_unicast+0x430/0x600
> netlink_sendmsg+0x8fa/0xd60
> sock_sendmsg+0xb1/0xe0
> ___sys_sendmsg+0x678/0x980
> __sys_sendmsg+0xc4/0x210
> do_syscall_64+0x232/0x7f0
> return_from_SYSCALL_64+0x0/0x75
>
> Freed by task 112:
> kasan_slab_free+0x71/0xc0
> kfree+0x114/0x320
> rcu_process_callbacks+0xc3f/0x1600
> __do_softirq+0x2bf/0xc06
>
> The buggy address belongs to the object at ffff881b83dae600
> which belongs to the cache kmalloc-4096 of size 4096
> The buggy address is located 24 bytes inside of
> 4096-byte region [ffff881b83dae600, ffff881b83daf600)
> The buggy address belongs to the page:
> page:ffffea006e0f6a00 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0
> flags: 0x17ffffc0008100(slab|head)
> raw: 0017ffffc0008100 0000000000000000 0000000000000000 0000000100070007
> raw: dead000000000100 dead000000000200 ffff880187c0e600 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff881b83dae500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff881b83dae580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >ffff881b83dae600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff881b83dae680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff881b83dae700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
> The problem is that the htnode is freed before the linked knodes and the
> latter will try to access the first at u32_destroy_key() time.
> This change addresses the issue using the htnode refcnt to guarantee
> the correct free order. While at it also add a RCU annotation,
> to keep sparse happy.
>
> v1 -> v2: use rtnl_derefence() instead of RCU read locks
>
> Reported-by: Li Shuang <shuali@redhat.com>
> Fixes: c0d378ef1266 ("net_sched: use tcf_queue_work() in u32 filter")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> net/sched/cls_u32.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
> index 60c892c36a60..10440fbf3c68 100644
> --- a/net/sched/cls_u32.c
> +++ b/net/sched/cls_u32.c
> @@ -398,10 +398,12 @@ static int u32_init(struct tcf_proto *tp)
> static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n,
> bool free_pf)
> {
> + struct tc_u_hnode *ht = rtnl_dereference(n->ht_down);
> +
> tcf_exts_destroy(&n->exts);
> tcf_exts_put_net(&n->exts);
> - if (n->ht_down)
> - n->ht_down->refcnt--;
> + if (ht && ht->refcnt-- == 0)
> + kfree(ht);
> #ifdef CONFIG_CLS_U32_PERF
> if (free_pf)
> free_percpu(n->pf);
> @@ -624,7 +626,12 @@ static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
> idr_destroy(&ht->handle_idr);
> idr_remove_ext(&tp_c->handle_idr, ht->handle);
> RCU_INIT_POINTER(*hn, ht->next);
> - kfree_rcu(ht, rcu);
> +
> + /* u32_destroy_key() will will later free ht for us, if
> + * it's still referenced by some knode
> + */
> + if (ht->refcnt == 0)
> + kfree_rcu(ht, rcu);
> return 0;
> }
> }
> @@ -667,7 +674,11 @@ static void u32_destroy(struct tcf_proto *tp, struct netlink_ext_ack *extack)
>
> while ((ht = rtnl_dereference(tp_c->hlist)) != NULL) {
> RCU_INIT_POINTER(tp_c->hlist, ht->next);
> - kfree_rcu(ht, rcu);
> + /* u32_destroy_key() will will later free ht for us, if
> + * it's still referenced by some knode
> + */
> + if (ht->refcnt == 0)
> + kfree_rcu(ht, rcu);
> }
>
> idr_destroy(&tp_c->handle_idr);
>
Good catch, Paolo.
Tested-by: Ivan Vecera <ivecera@redhat.com>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH net v2] cls_u32: fix use after free in u32_destroy_key()
2018-02-02 14:30 ` [PATCH net v2] " Paolo Abeni
2018-02-02 17:54 ` Ivan Vecera
@ 2018-02-02 21:52 ` Cong Wang
2018-02-03 17:46 ` Paolo Abeni
2018-02-03 18:49 ` Paolo Abeni
2 siblings, 1 reply; 7+ messages in thread
From: Cong Wang @ 2018-02-02 21:52 UTC (permalink / raw)
To: Paolo Abeni
Cc: Linux Kernel Network Developers, David S. Miller,
Jamal Hadi Salim, Jiri Pirko, Li Shuang
On Fri, Feb 2, 2018 at 6:30 AM, Paolo Abeni <pabeni@redhat.com> wrote:
> The problem is that the htnode is freed before the linked knodes and the
> latter will try to access the first at u32_destroy_key() time.
> This change addresses the issue using the htnode refcnt to guarantee
> the correct free order. While at it also add a RCU annotation,
> to keep sparse happy.
>
> v1 -> v2: use rtnl_derefence() instead of RCU read locks
>
> Reported-by: Li Shuang <shuali@redhat.com>
> Fixes: c0d378ef1266 ("net_sched: use tcf_queue_work() in u32 filter")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> net/sched/cls_u32.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
> index 60c892c36a60..10440fbf3c68 100644
> --- a/net/sched/cls_u32.c
> +++ b/net/sched/cls_u32.c
> @@ -398,10 +398,12 @@ static int u32_init(struct tcf_proto *tp)
> static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n,
> bool free_pf)
> {
> + struct tc_u_hnode *ht = rtnl_dereference(n->ht_down);
> +
> tcf_exts_destroy(&n->exts);
> tcf_exts_put_net(&n->exts);
> - if (n->ht_down)
> - n->ht_down->refcnt--;
> + if (ht && ht->refcnt-- == 0)
> + kfree(ht);
> #ifdef CONFIG_CLS_U32_PERF
> if (free_pf)
> free_percpu(n->pf);
> @@ -624,7 +626,12 @@ static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
> idr_destroy(&ht->handle_idr);
> idr_remove_ext(&tp_c->handle_idr, ht->handle);
> RCU_INIT_POINTER(*hn, ht->next);
> - kfree_rcu(ht, rcu);
> +
> + /* u32_destroy_key() will will later free ht for us, if
> + * it's still referenced by some knode
> + */
> + if (ht->refcnt == 0)
> + kfree_rcu(ht, rcu);
Isn't u32_destroy_hnode() always called with ht->refcnt==0 ?
So no need this check at all?
> return 0;
> }
> }
> @@ -667,7 +674,11 @@ static void u32_destroy(struct tcf_proto *tp, struct netlink_ext_ack *extack)
>
> while ((ht = rtnl_dereference(tp_c->hlist)) != NULL) {
> RCU_INIT_POINTER(tp_c->hlist, ht->next);
> - kfree_rcu(ht, rcu);
> + /* u32_destroy_key() will will later free ht for us, if
Nit: double "will"
> + * it's still referenced by some knode
> + */
> + if (ht->refcnt == 0)
> + kfree_rcu(ht, rcu);
This part looks fine.
Thanks!
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH net v2] cls_u32: fix use after free in u32_destroy_key()
2018-02-02 21:52 ` Cong Wang
@ 2018-02-03 17:46 ` Paolo Abeni
0 siblings, 0 replies; 7+ messages in thread
From: Paolo Abeni @ 2018-02-03 17:46 UTC (permalink / raw)
To: Cong Wang
Cc: Linux Kernel Network Developers, David S. Miller,
Jamal Hadi Salim, Jiri Pirko, Li Shuang, Ivan Vecera
Hi,
On Fri, 2018-02-02 at 13:52 -0800, Cong Wang wrote:
> On Fri, Feb 2, 2018 at 6:30 AM, Paolo Abeni <pabeni@redhat.com> wrote:
> > The problem is that the htnode is freed before the linked knodes and the
> > latter will try to access the first at u32_destroy_key() time.
> > This change addresses the issue using the htnode refcnt to guarantee
> > the correct free order. While at it also add a RCU annotation,
> > to keep sparse happy.
> >
> > v1 -> v2: use rtnl_derefence() instead of RCU read locks
> >
> > Reported-by: Li Shuang <shuali@redhat.com>
> > Fixes: c0d378ef1266 ("net_sched: use tcf_queue_work() in u32 filter")
> > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> > ---
> > net/sched/cls_u32.c | 19 +++++++++++++++----
> > 1 file changed, 15 insertions(+), 4 deletions(-)
> >
> > diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
> > index 60c892c36a60..10440fbf3c68 100644
> > --- a/net/sched/cls_u32.c
> > +++ b/net/sched/cls_u32.c
> > @@ -398,10 +398,12 @@ static int u32_init(struct tcf_proto *tp)
> > static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n,
> > bool free_pf)
> > {
> > + struct tc_u_hnode *ht = rtnl_dereference(n->ht_down);
> > +
> > tcf_exts_destroy(&n->exts);
> > tcf_exts_put_net(&n->exts);
> > - if (n->ht_down)
> > - n->ht_down->refcnt--;
> > + if (ht && ht->refcnt-- == 0)
> > + kfree(ht);
> > #ifdef CONFIG_CLS_U32_PERF
> > if (free_pf)
> > free_percpu(n->pf);
> > @@ -624,7 +626,12 @@ static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
> > idr_destroy(&ht->handle_idr);
> > idr_remove_ext(&tp_c->handle_idr, ht->handle);
> > RCU_INIT_POINTER(*hn, ht->next);
> > - kfree_rcu(ht, rcu);
> > +
> > + /* u32_destroy_key() will will later free ht for us, if
> > + * it's still referenced by some knode
> > + */
> > + if (ht->refcnt == 0)
> > + kfree_rcu(ht, rcu);
>
>
> Isn't u32_destroy_hnode() always called with ht->refcnt==0 ?
> So no need this check at all?
>
>
> > return 0;
> > }
> > }
> > @@ -667,7 +674,11 @@ static void u32_destroy(struct tcf_proto *tp, struct netlink_ext_ack *extack)
> >
> > while ((ht = rtnl_dereference(tp_c->hlist)) != NULL) {
> > RCU_INIT_POINTER(tp_c->hlist, ht->next);
> > - kfree_rcu(ht, rcu);
> > + /* u32_destroy_key() will will later free ht for us, if
>
>
> Nit: double "will"
>
>
> > + * it's still referenced by some knode
> > + */
> > + if (ht->refcnt == 0)
> > + kfree_rcu(ht, rcu);
>
>
> This part looks fine.
>
> Thanks!
Thank you for the feedback!
I will send a v3 soon, after some testing.
Cheers,
Paolo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH net v2] cls_u32: fix use after free in u32_destroy_key()
2018-02-02 14:30 ` [PATCH net v2] " Paolo Abeni
2018-02-02 17:54 ` Ivan Vecera
2018-02-02 21:52 ` Cong Wang
@ 2018-02-03 18:49 ` Paolo Abeni
2 siblings, 0 replies; 7+ messages in thread
From: Paolo Abeni @ 2018-02-03 18:49 UTC (permalink / raw)
To: netdev
Cc: David S. Miller, Jamal Hadi Salim, Cong Wang, Jiri Pirko, Li Shuang
On Fri, 2018-02-02 at 15:30 +0100, Paolo Abeni wrote:
> Li Shuang reported an Oops with cls_u32 due to an use-after-free
> in u32_destroy_key(). The use-after-free can be triggered with:
>
> dev=lo
> tc qdisc add dev $dev root handle 1: htb default 10
> tc filter add dev $dev parent 1: prio 5 handle 1: protocol ip u32 divisor 256
> tc filter add dev $dev protocol ip parent 1: prio 5 u32 ht 800:: match ip dst\
> 10.0.0.0/8 hashkey mask 0x0000ff00 at 16 link 1:
> tc qdisc del dev $dev root
>
> Which causes the following kasan splat:
>
> ==================================================================
> BUG: KASAN: use-after-free in u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
> Read of size 4 at addr ffff881b83dae618 by task kworker/u48:5/571
>
> CPU: 17 PID: 571 Comm: kworker/u48:5 Not tainted 4.15.0+ #87
> Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.1.7 06/16/2016
> Workqueue: tc_filter_workqueue u32_delete_key_freepf_work [cls_u32]
> Call Trace:
> dump_stack+0xd6/0x182
> ? dma_virt_map_sg+0x22e/0x22e
> print_address_description+0x73/0x290
> kasan_report+0x277/0x360
> ? u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
> u32_destroy_key.constprop.21+0x117/0x140 [cls_u32]
> u32_delete_key_freepf_work+0x1c/0x30 [cls_u32]
> process_one_work+0xae0/0x1c80
> ? sched_clock+0x5/0x10
> ? pwq_dec_nr_in_flight+0x3c0/0x3c0
> ? _raw_spin_unlock_irq+0x29/0x40
> ? trace_hardirqs_on_caller+0x381/0x570
> ? _raw_spin_unlock_irq+0x29/0x40
> ? finish_task_switch+0x1e5/0x760
> ? finish_task_switch+0x208/0x760
> ? preempt_notifier_dec+0x20/0x20
> ? __schedule+0x839/0x1ee0
> ? check_noncircular+0x20/0x20
> ? firmware_map_remove+0x73/0x73
> ? find_held_lock+0x39/0x1c0
> ? worker_thread+0x434/0x1820
> ? lock_contended+0xee0/0xee0
> ? lock_release+0x1100/0x1100
> ? init_rescuer.part.16+0x150/0x150
> ? retint_kernel+0x10/0x10
> worker_thread+0x216/0x1820
> ? process_one_work+0x1c80/0x1c80
> ? lock_acquire+0x1a5/0x540
> ? lock_downgrade+0x6b0/0x6b0
> ? sched_clock+0x5/0x10
> ? lock_release+0x1100/0x1100
> ? compat_start_thread+0x80/0x80
> ? do_raw_spin_trylock+0x190/0x190
> ? _raw_spin_unlock_irq+0x29/0x40
> ? trace_hardirqs_on_caller+0x381/0x570
> ? _raw_spin_unlock_irq+0x29/0x40
> ? finish_task_switch+0x1e5/0x760
> ? finish_task_switch+0x208/0x760
> ? preempt_notifier_dec+0x20/0x20
> ? __schedule+0x839/0x1ee0
> ? kmem_cache_alloc_trace+0x143/0x320
> ? firmware_map_remove+0x73/0x73
> ? sched_clock+0x5/0x10
> ? sched_clock_cpu+0x18/0x170
> ? find_held_lock+0x39/0x1c0
> ? schedule+0xf3/0x3b0
> ? lock_downgrade+0x6b0/0x6b0
> ? __schedule+0x1ee0/0x1ee0
> ? do_wait_intr_irq+0x340/0x340
> ? do_raw_spin_trylock+0x190/0x190
> ? _raw_spin_unlock_irqrestore+0x32/0x60
> ? process_one_work+0x1c80/0x1c80
> ? process_one_work+0x1c80/0x1c80
> kthread+0x312/0x3d0
> ? kthread_create_worker_on_cpu+0xc0/0xc0
> ret_from_fork+0x3a/0x50
>
> Allocated by task 1688:
> kasan_kmalloc+0xa0/0xd0
> __kmalloc+0x162/0x380
> u32_change+0x1220/0x3c9e [cls_u32]
> tc_ctl_tfilter+0x1ba6/0x2f80
> rtnetlink_rcv_msg+0x4f0/0x9d0
> netlink_rcv_skb+0x124/0x320
> netlink_unicast+0x430/0x600
> netlink_sendmsg+0x8fa/0xd60
> sock_sendmsg+0xb1/0xe0
> ___sys_sendmsg+0x678/0x980
> __sys_sendmsg+0xc4/0x210
> do_syscall_64+0x232/0x7f0
> return_from_SYSCALL_64+0x0/0x75
>
> Freed by task 112:
> kasan_slab_free+0x71/0xc0
> kfree+0x114/0x320
> rcu_process_callbacks+0xc3f/0x1600
> __do_softirq+0x2bf/0xc06
>
> The buggy address belongs to the object at ffff881b83dae600
> which belongs to the cache kmalloc-4096 of size 4096
> The buggy address is located 24 bytes inside of
> 4096-byte region [ffff881b83dae600, ffff881b83daf600)
> The buggy address belongs to the page:
> page:ffffea006e0f6a00 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0
> flags: 0x17ffffc0008100(slab|head)
> raw: 0017ffffc0008100 0000000000000000 0000000000000000 0000000100070007
> raw: dead000000000100 dead000000000200 ffff880187c0e600 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff881b83dae500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff881b83dae580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >ffff881b83dae600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff881b83dae680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff881b83dae700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
> The problem is that the htnode is freed before the linked knodes and the
> latter will try to access the first at u32_destroy_key() time.
> This change addresses the issue using the htnode refcnt to guarantee
> the correct free order. While at it also add a RCU annotation,
> to keep sparse happy.
>
> v1 -> v2: use rtnl_derefence() instead of RCU read locks
>
> Reported-by: Li Shuang <shuali@redhat.com>
> Fixes: c0d378ef1266 ("net_sched: use tcf_queue_work() in u32 filter")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> net/sched/cls_u32.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
> index 60c892c36a60..10440fbf3c68 100644
> --- a/net/sched/cls_u32.c
> +++ b/net/sched/cls_u32.c
> @@ -398,10 +398,12 @@ static int u32_init(struct tcf_proto *tp)
> static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n,
> bool free_pf)
> {
> + struct tc_u_hnode *ht = rtnl_dereference(n->ht_down);
> +
> tcf_exts_destroy(&n->exts);
> tcf_exts_put_net(&n->exts);
> - if (n->ht_down)
> - n->ht_down->refcnt--;
> + if (ht && ht->refcnt-- == 0)
oops... this ^^^^^^^^^^^^ should be: '--th->refcnt' ...
>
> + kfree(ht);
#ifdef CONFIG_CLS_U32_PERF
> if (free_pf)
> free_percpu(n->pf);
> @@ -624,7 +626,12 @@ static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
> idr_destroy(&ht->handle_idr);
> idr_remove_ext(&tp_c->handle_idr, ht->handle);
> RCU_INIT_POINTER(*hn, ht->next);
> - kfree_rcu(ht, rcu);
> +
> + /* u32_destroy_key() will will later free ht for us, if
> + * it's still referenced by some knode
> + */
> + if (ht->refcnt == 0)
> + kfree_rcu(ht, rcu);
> return 0;
> }
> }
> @@ -667,7 +674,11 @@ static void u32_destroy(struct tcf_proto *tp, struct netlink_ext_ack *extack)
>
> while ((ht = rtnl_dereference(tp_c->hlist)) != NULL) {
> RCU_INIT_POINTER(tp_c->hlist, ht->next);
> - kfree_rcu(ht, rcu);
> + /* u32_destroy_key() will will later free ht for us, if
> + * it's still referenced by some knode
> + */
> + if (ht->refcnt == 0)
> + kfree_rcu(ht, rcu);
And it's probably better merge the previous loop with this one.
I'll include the above changes in v3
Paolo
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2018-02-03 18:49 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-02-02 13:20 [PATCH net] cls_u32: fix use after free in u32_destroy_key() Paolo Abeni
2018-02-02 13:35 ` Paolo Abeni
2018-02-02 14:30 ` [PATCH net v2] " Paolo Abeni
2018-02-02 17:54 ` Ivan Vecera
2018-02-02 21:52 ` Cong Wang
2018-02-03 17:46 ` Paolo Abeni
2018-02-03 18:49 ` Paolo Abeni
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).