ACK/Cmnt[B/C]: [PATCH 1/1] net: rds: force to destroy connection if t_sock is NULL in rds_tcp_kill_sock().

Stefan Bader stefan.bader at canonical.com
Fri Jun 28 12:08:51 UTC 2019 

On 04.06.19 08:47, Thomas Lamprecht wrote:
> From: Mao Wenan <maowenan at huawei.com>
> 
> CVE-2019-11815
> https://people.canonical.com/~ubuntu-security/cve/2019/CVE-2019-11815.html
> 
> When it is to cleanup net namespace, rds_tcp_exit_net() will call
> rds_tcp_kill_sock(), if t_sock is NULL, it will not call
> rds_conn_destroy(), rds_conn_path_destroy() and rds_tcp_conn_free() to free
> connection, and the worker cp_conn_w is not stopped, afterwards the net is freed in
> net_drop_ns(); While cp_conn_w rds_connect_worker() will call rds_tcp_conn_path_connect()
> and reference 'net' which has already been freed.
> 
> In rds_tcp_conn_path_connect(), rds_tcp_set_callbacks() will set t_sock = sock before
> sock->ops->connect, but if connect() is failed, it will call
> rds_tcp_restore_callbacks() and set t_sock = NULL, if connect is always
> failed, rds_connect_worker() will try to reconnect all the time, so
> rds_tcp_kill_sock() will never to cancel worker cp_conn_w and free the
> connections.
> 
> Therefore, the condition !tc->t_sock is not needed if it is going to do
> cleanup_net->rds_tcp_exit_net->rds_tcp_kill_sock, because tc->t_sock is always
> NULL, and there is on other path to cancel cp_conn_w and free
> connection. So this patch is to fix this.
> 
> rds_tcp_kill_sock():
> ...
> if (net != c_net || !tc->t_sock)
> ...
> Acked-by: Santosh Shilimkar <santosh.shilimkar at oracle.com>
> 
> ==================================================================
> BUG: KASAN: use-after-free in inet_create+0xbcc/0xd28
> net/ipv4/af_inet.c:340
> Read of size 4 at addr ffff8003496a4684 by task kworker/u8:4/3721
> 
> CPU: 3 PID: 3721 Comm: kworker/u8:4 Not tainted 5.1.0 #11
> Hardware name: linux,dummy-virt (DT)
> Workqueue: krdsd rds_connect_worker
> Call trace:
>  dump_backtrace+0x0/0x3c0 arch/arm64/kernel/time.c:53
>  show_stack+0x28/0x38 arch/arm64/kernel/traps.c:152
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x120/0x188 lib/dump_stack.c:113
>  print_address_description+0x68/0x278 mm/kasan/report.c:253
>  kasan_report_error mm/kasan/report.c:351 [inline]
>  kasan_report+0x21c/0x348 mm/kasan/report.c:409
>  __asan_report_load4_noabort+0x30/0x40 mm/kasan/report.c:429
>  inet_create+0xbcc/0xd28 net/ipv4/af_inet.c:340
>  __sock_create+0x4f8/0x770 net/socket.c:1276
>  sock_create_kern+0x50/0x68 net/socket.c:1322
>  rds_tcp_conn_path_connect+0x2b4/0x690 net/rds/tcp_connect.c:114
>  rds_connect_worker+0x108/0x1d0 net/rds/threads.c:175
>  process_one_work+0x6e8/0x1700 kernel/workqueue.c:2153
>  worker_thread+0x3b0/0xdd0 kernel/workqueue.c:2296
>  kthread+0x2f0/0x378 kernel/kthread.c:255
>  ret_from_fork+0x10/0x18 arch/arm64/kernel/entry.S:1117
> 
> Allocated by task 687:
>  save_stack mm/kasan/kasan.c:448 [inline]
>  set_track mm/kasan/kasan.c:460 [inline]
>  kasan_kmalloc+0xd4/0x180 mm/kasan/kasan.c:553
>  kasan_slab_alloc+0x14/0x20 mm/kasan/kasan.c:490
>  slab_post_alloc_hook mm/slab.h:444 [inline]
>  slab_alloc_node mm/slub.c:2705 [inline]
>  slab_alloc mm/slub.c:2713 [inline]
>  kmem_cache_alloc+0x14c/0x388 mm/slub.c:2718
>  kmem_cache_zalloc include/linux/slab.h:697 [inline]
>  net_alloc net/core/net_namespace.c:384 [inline]
>  copy_net_ns+0xc4/0x2d0 net/core/net_namespace.c:424
>  create_new_namespaces+0x300/0x658 kernel/nsproxy.c:107
>  unshare_nsproxy_namespaces+0xa0/0x198 kernel/nsproxy.c:206
>  ksys_unshare+0x340/0x628 kernel/fork.c:2577
>  __do_sys_unshare kernel/fork.c:2645 [inline]
>  __se_sys_unshare kernel/fork.c:2643 [inline]
>  __arm64_sys_unshare+0x38/0x58 kernel/fork.c:2643
>  __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
>  invoke_syscall arch/arm64/kernel/syscall.c:47 [inline]
>  el0_svc_common+0x168/0x390 arch/arm64/kernel/syscall.c:83
>  el0_svc_handler+0x60/0xd0 arch/arm64/kernel/syscall.c:129
>  el0_svc+0x8/0xc arch/arm64/kernel/entry.S:960
> 
> Freed by task 264:
>  save_stack mm/kasan/kasan.c:448 [inline]
>  set_track mm/kasan/kasan.c:460 [inline]
>  __kasan_slab_free+0x114/0x220 mm/kasan/kasan.c:521
>  kasan_slab_free+0x10/0x18 mm/kasan/kasan.c:528
>  slab_free_hook mm/slub.c:1370 [inline]
>  slab_free_freelist_hook mm/slub.c:1397 [inline]
>  slab_free mm/slub.c:2952 [inline]
>  kmem_cache_free+0xb8/0x3a8 mm/slub.c:2968
>  net_free net/core/net_namespace.c:400 [inline]
>  net_drop_ns.part.6+0x78/0x90 net/core/net_namespace.c:407
>  net_drop_ns net/core/net_namespace.c:406 [inline]
>  cleanup_net+0x53c/0x6d8 net/core/net_namespace.c:569
>  process_one_work+0x6e8/0x1700 kernel/workqueue.c:2153
>  worker_thread+0x3b0/0xdd0 kernel/workqueue.c:2296
>  kthread+0x2f0/0x378 kernel/kthread.c:255
>  ret_from_fork+0x10/0x18 arch/arm64/kernel/entry.S:1117
> 
> The buggy address belongs to the object at ffff8003496a3f80
>  which belongs to the cache net_namespace of size 7872
> The buggy address is located 1796 bytes inside of
>  7872-byte region [ffff8003496a3f80, ffff8003496a5e40)
> The buggy address belongs to the page:
> page:ffff7e000d25a800 count:1 mapcount:0 mapping:ffff80036ce4b000
> index:0x0 compound_mapcount: 0
> flags: 0xffffe0000008100(slab|head)
> raw: 0ffffe0000008100 dead000000000100 dead000000000200 ffff80036ce4b000
> raw: 0000000000000000 0000000080040004 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff8003496a4580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8003496a4600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ffff8003496a4680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                    ^
>  ffff8003496a4700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8003496a4780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> Fixes: 467fa15356ac("RDS-TCP: Support multiple RDS-TCP listen endpoints, one per netns.")
> Reported-by: Hulk Robot <hulkci at huawei.com>
> Signed-off-by: Mao Wenan <maowenan at huawei.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> (cherry picked from commit cb66ddd156203daefb8d71158036b27b0e2caf63)
> Signed-off-by: Thomas Lamprecht <t.lamprecht at proxmox.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---

As Connor mentioned this is also marked as required for Cosmic and since it
seems to apply without changes, too, we should get it into both.

-Stefan

>  net/rds/tcp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/rds/tcp.c b/net/rds/tcp.c
> index 4df21e47d2ab..0a31fa6ef752 100644
> --- a/net/rds/tcp.c
> +++ b/net/rds/tcp.c
> @@ -531,7 +531,7 @@ static void rds_tcp_kill_sock(struct net *net)
>  	list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {
>  		struct net *c_net = read_pnet(&tc->t_cpath->cp_conn->c_net);
>  
> -		if (net != c_net || !tc->t_sock)
> +		if (net != c_net)
>  			continue;
>  		if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn)) {
>  			list_move_tail(&tc->t_tcp_node, &tmp_list);
> 


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