* [patch net-next] net: sched: fix use-after-free in tcf_block_put_ext
@ 2017-12-08 18:27 Jiri Pirko
2017-12-08 19:10 ` David Miller
2017-12-08 20:05 ` Cong Wang
0 siblings, 2 replies; 3+ messages in thread
From: Jiri Pirko @ 2017-12-08 18:27 UTC (permalink / raw)
To: netdev; +Cc: davem, jhs, xiyou.wangcong, mlxsw, code
From: Jiri Pirko <jiri@mellanox.com>
Since the block is freed with last chain being put, once we reach the
end of iteration of list_for_each_entry_safe, the block may be
already freed. I'm hitting this only by creating and deleting clsact:
[ 202.171952] ==================================================================
[ 202.180182] BUG: KASAN: use-after-free in tcf_block_put_ext+0x240/0x390
[ 202.187590] Read of size 8 at addr ffff880225539a80 by task tc/796
[ 202.194508]
[ 202.196185] CPU: 0 PID: 796 Comm: tc Not tainted 4.15.0-rc2jiri+ #5
[ 202.203200] Hardware name: Mellanox Technologies Ltd. "MSN2100-CB2F"/"SA001017", BIOS 5.6.5 06/07/2016
[ 202.213613] Call Trace:
[ 202.216369] dump_stack+0xda/0x169
[ 202.220192] ? dma_virt_map_sg+0x147/0x147
[ 202.224790] ? show_regs_print_info+0x54/0x54
[ 202.229691] ? tcf_chain_destroy+0x1dc/0x250
[ 202.234494] print_address_description+0x83/0x3d0
[ 202.239781] ? tcf_block_put_ext+0x240/0x390
[ 202.244575] kasan_report+0x1ba/0x460
[ 202.248707] ? tcf_block_put_ext+0x240/0x390
[ 202.253518] tcf_block_put_ext+0x240/0x390
[ 202.258117] ? tcf_chain_flush+0x290/0x290
[ 202.262708] ? qdisc_hash_del+0x82/0x1a0
[ 202.267111] ? qdisc_hash_add+0x50/0x50
[ 202.271411] ? __lock_is_held+0x5f/0x1a0
[ 202.275843] clsact_destroy+0x3d/0x80 [sch_ingress]
[ 202.281323] qdisc_destroy+0xcb/0x240
[ 202.285445] qdisc_graft+0x216/0x7b0
[ 202.289497] tc_get_qdisc+0x260/0x560
Fix this by holding the block also by chain 0 and put chain 0
explicitly, out of the list_for_each_entry_safe loop at the very
end of tcf_block_put_ext.
Fixes: efbf78973978 ("net_sched: get rid of rcu_barrier() in tcf_block_put_ext()")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
---
net/sched/cls_api.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index d51051d..5b9b8a6 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -342,23 +342,24 @@ void tcf_block_put_ext(struct tcf_block *block, struct Qdisc *q,
{
struct tcf_chain *chain, *tmp;
- /* Hold a refcnt for all chains, except 0, so that they don't disappear
+ /* Hold a refcnt for all chains, so that they don't disappear
* while we are iterating.
*/
list_for_each_entry(chain, &block->chain_list, list)
- if (chain->index)
- tcf_chain_hold(chain);
+ tcf_chain_hold(chain);
list_for_each_entry(chain, &block->chain_list, list)
tcf_chain_flush(chain);
tcf_block_offload_unbind(block, q, ei);
- /* At this point, all the chains should have refcnt >= 1. Block will be
- * freed after all chains are gone.
- */
+ /* At this point, all the chains should have refcnt >= 1. */
list_for_each_entry_safe(chain, tmp, &block->chain_list, list)
tcf_chain_put(chain);
+
+ /* Finally, put chain 0 and allow block to be freed. */
+ chain = list_first_entry(&block->chain_list, struct tcf_chain, list);
+ tcf_chain_put(chain);
}
EXPORT_SYMBOL(tcf_block_put_ext);
--
2.9.5
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [patch net-next] net: sched: fix use-after-free in tcf_block_put_ext
2017-12-08 18:27 [patch net-next] net: sched: fix use-after-free in tcf_block_put_ext Jiri Pirko
@ 2017-12-08 19:10 ` David Miller
2017-12-08 20:05 ` Cong Wang
1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2017-12-08 19:10 UTC (permalink / raw)
To: jiri; +Cc: netdev, jhs, xiyou.wangcong, mlxsw, code
From: Jiri Pirko <jiri@resnulli.us>
Date: Fri, 8 Dec 2017 19:27:27 +0100
> From: Jiri Pirko <jiri@mellanox.com>
>
> Since the block is freed with last chain being put, once we reach the
> end of iteration of list_for_each_entry_safe, the block may be
> already freed. I'm hitting this only by creating and deleting clsact:
...
> Fix this by holding the block also by chain 0 and put chain 0
> explicitly, out of the list_for_each_entry_safe loop at the very
> end of tcf_block_put_ext.
>
> Fixes: efbf78973978 ("net_sched: get rid of rcu_barrier() in tcf_block_put_ext()")
> Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Applied, thanks Jiri.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [patch net-next] net: sched: fix use-after-free in tcf_block_put_ext
2017-12-08 18:27 [patch net-next] net: sched: fix use-after-free in tcf_block_put_ext Jiri Pirko
2017-12-08 19:10 ` David Miller
@ 2017-12-08 20:05 ` Cong Wang
1 sibling, 0 replies; 3+ messages in thread
From: Cong Wang @ 2017-12-08 20:05 UTC (permalink / raw)
To: Jiri Pirko
Cc: Linux Kernel Network Developers, David Miller, Jamal Hadi Salim,
mlxsw, Roman Kapl
On Fri, Dec 8, 2017 at 10:27 AM, Jiri Pirko <jiri@resnulli.us> wrote:
> From: Jiri Pirko <jiri@mellanox.com>
>
> Since the block is freed with last chain being put, once we reach the
> end of iteration of list_for_each_entry_safe, the block may be
> already freed. I'm hitting this only by creating and deleting clsact:
List is still too tricky to work with refcnt.
>
> [ 202.171952] ==================================================================
> [ 202.180182] BUG: KASAN: use-after-free in tcf_block_put_ext+0x240/0x390
I should enable KASAN now, otherwise can't catch this
even though I tested this code path for hundreds of times.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-12-08 18:27 [patch net-next] net: sched: fix use-after-free in tcf_block_put_ext Jiri Pirko
2017-12-08 19:10 ` David Miller
2017-12-08 20:05 ` Cong Wang
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