Hi Jon,
Below solution does not fully resolve the issue. I'm finding out another
solution.
Regards,
Hoang
-----Original Message-----
From: Jon Maloy <jma...@redhat.com>
Sent: Tuesday, September 1, 2020 8:53 PM
To: Hoang Huu Le <hoang.h...@dektech.com.au>; ma...@donjonn.com;
ying....@windriver.com; tipc-discussion@lists.sourceforge.net
Cc: syzbot+6ea1f7a8df64596ef...@syzkaller.appspotmail.com;
syzbot+e9cc557752ab126c1...@syzkaller.appspotmail.com
Subject: Re: [PATCH] tipc: fix use-after-free in tipc_bcast_get_mode
On 8/25/20 11:52 PM, Hoang Huu Le wrote:
> Syzbot has reported those issues as:
>
> ==================================================================
> BUG: KASAN: use-after-free in tipc_bcast_get_mode+0x3ab/0x400
> net/tipc/bcast.c:759
> Read of size 1 at addr ffff88805e6b3571 by task kworker/0:6/3850
>
> CPU: 0 PID: 3850 Comm: kworker/0:6 Not tainted 5.8.0-rc7-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Workqueue: events tipc_net_finalize_work
>
> Thread 1's call trace:
> [...]
> kfree+0x103/0x2c0 mm/slab.c:3757 <- bcbase releasing
> tipc_bcast_stop+0x1b0/0x2f0 net/tipc/bcast.c:721
> tipc_exit_net+0x24/0x270 net/tipc/core.c:112
> [...]
>
> Thread 2's call trace:
> [...]
> tipc_bcast_get_mode+0x3ab/0x400 net/tipc/bcast.c:759 <- bcbase
> has already been freed by Thread 1
>
> tipc_node_broadcast+0x9e/0xcc0 net/tipc/node.c:1744
> tipc_nametbl_publish+0x60b/0x970 net/tipc/name_table.c:752
> tipc_net_finalize net/tipc/net.c:141 [inline]
> tipc_net_finalize+0x1fa/0x310 net/tipc/net.c:131
> tipc_net_finalize_work+0x55/0x80 net/tipc/net.c:150
> [...]
>
> ==================================================================
> BUG: KASAN: use-after-free in tipc_named_reinit+0xef/0x290
> net/tipc/name_distr.c:344
> Read of size 8 at addr ffff888052ab2000 by task kworker/0:13/30628
> CPU: 0 PID: 30628 Comm: kworker/0:13 Not tainted 5.8.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Workqueue: events tipc_net_finalize_work
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x1f0/0x31e lib/dump_stack.c:118
> print_address_description+0x66/0x5a0 mm/kasan/report.c:383
> __kasan_report mm/kasan/report.c:513 [inline]
> kasan_report+0x132/0x1d0 mm/kasan/report.c:530
> tipc_named_reinit+0xef/0x290 net/tipc/name_distr.c:344
> tipc_net_finalize+0x85/0xe0 net/tipc/net.c:138
> tipc_net_finalize_work+0x50/0x70 net/tipc/net.c:150
> process_one_work+0x789/0xfc0 kernel/workqueue.c:2269
> worker_thread+0xaa4/0x1460 kernel/workqueue.c:2415
> kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
> [...]
> Freed by task 14058:
> save_stack mm/kasan/common.c:48 [inline]
> set_track mm/kasan/common.c:56 [inline]
> kasan_set_free_info mm/kasan/common.c:316 [inline]
> __kasan_slab_free+0x114/0x170 mm/kasan/common.c:455
> __cache_free mm/slab.c:3426 [inline]
> kfree+0x10a/0x220 mm/slab.c:3757
> tipc_exit_net+0x29/0x50 net/tipc/core.c:113
> ops_exit_list net/core/net_namespace.c:186 [inline]
> cleanup_net+0x708/0xba0 net/core/net_namespace.c:603
> process_one_work+0x789/0xfc0 kernel/workqueue.c:2269
> worker_thread+0xaa4/0x1460 kernel/workqueue.c:2415
> kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
>
> Solution 1 (preferer):
> Fix it by calling flush_scheduled_work() to make sure the
> tipc_net_finalize_work() stopped before releasing bcbase object.
>
> Solution 2:
> Fix it by introducing a bit flag and returning if flag is zero
> (object had already been freed)
>
> Reported-by: syzbot+6ea1f7a8df64596ef...@syzkaller.appspotmail.com
> Reported-by: syzbot+e9cc557752ab126c1...@syzkaller.appspotmail.com
> Signed-off-by: Hoang Huu Le <hoang.h...@dektech.com.au>
> ---
> net/tipc/bcast.c | 1 +
> net/tipc/core.c | 1 +
> net/tipc/core.h | 1 +
> net/tipc/net.c | 3 +++
> 4 files changed, 6 insertions(+)
>
> diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c
> index 940d176e0e87..56b624c8b6d4 100644
> --- a/net/tipc/bcast.c
> +++ b/net/tipc/bcast.c
> @@ -718,6 +718,7 @@ void tipc_bcast_stop(struct net *net)
> struct tipc_net *tn = net_generic(net, tipc_net_id);
>
> synchronize_net();
> + clear_bit_unlock(0, &tn->net_exit_flag);
> kfree(tn->bcbase);
> kfree(tn->bcl);
> }
> diff --git a/net/tipc/core.c b/net/tipc/core.c
> index 4f6dc74adf45..93ea7dc05bf2 100644
> --- a/net/tipc/core.c
> +++ b/net/tipc/core.c
> @@ -60,6 +60,7 @@ static int __net_init tipc_init_net(struct net *net)
> tn->trial_addr = 0;
> tn->addr_trial_end = 0;
> tn->capabilities = TIPC_NODE_CAPABILITIES;
> + test_and_set_bit_lock(0, &tn->net_exit_flag);
> memset(tn->node_id, 0, sizeof(tn->node_id));
> memset(tn->node_id_string, 0, sizeof(tn->node_id_string));
> tn->mon_threshold = TIPC_DEF_MON_THRESHOLD;
> diff --git a/net/tipc/core.h b/net/tipc/core.h
> index 631d83c9705f..aa75882dd932 100644
> --- a/net/tipc/core.h
> +++ b/net/tipc/core.h
> @@ -143,6 +143,7 @@ struct tipc_net {
> /* TX crypto handler */
> struct tipc_crypto *crypto_tx;
> #endif
> + unsigned long net_exit_flag;
> };
>
> static inline struct tipc_net *tipc_net(struct net *net)
> diff --git a/net/tipc/net.c b/net/tipc/net.c
> index 85400e4242de..0dcbfcff5ad3 100644
> --- a/net/tipc/net.c
> +++ b/net/tipc/net.c
> @@ -132,6 +132,9 @@ static void tipc_net_finalize(struct net *net, u32 addr)
> {
> struct tipc_net *tn = tipc_net(net);
>
> + if (unlikely(!test_bit(0, &tn->net_exit_flag)))
> + return;
> +
> if (cmpxchg(&tn->node_addr, 0, addr))
> return;
> tipc_set_node_addr(net, addr);
This solution should not cause any deadlocks, I hope.
Acked-by: Jon Maloy <jma...@redhat.com>
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