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SubjectRe: [PATCH net] net: rds: force to destroy connection if t_sock is NULL in rds_tcp_kill_sock().
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On 3/28/2019 2:10 AM, Mao Wenan wrote:
> 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)
> ...
> ==================================================================
> 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@huawei.com>
> Signed-off-by: Mao Wenan <maowenan@huawei.com>
> ---
Looks reasonable fix to me. Thanks !!

Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

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