Date:   Mon, 19 Nov 2018 17:31:03 +0900
From:   Xin Long <lucien.xin@...il.com>
To:     syzbot+aad231d51b1923158444@...kaller.appspotmail.com
Cc:     davem <davem@...emloft.net>, LKML <linux-kernel@...r.kernel.org>,
        linux-sctp@...r.kernel.org,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        network dev <netdev@...r.kernel.org>,
        Neil Horman <nhorman@...driver.com>,
        syzkaller-bugs@...glegroups.com,
        Vlad Yasevich <vyasevich@...il.com>
Subject: Re: KASAN: use-after-free Read in sctp_epaddr_lookup_transport

On Sat, Nov 17, 2018 at 10:59 AM syzbot
<syzbot+aad231d51b1923158444@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    a97b95653383 drivers/net/ethernet/qlogic/qed/qed_rdma.h: f..
> git tree:       net
> console output: https://syzkaller.appspot.com/x/log.txt?x=1217d26d400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d86f24333880b605
> dashboard link: https://syzkaller.appspot.com/bug?extid=aad231d51b1923158444
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13b5bb0b400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+aad231d51b1923158444@...kaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: use-after-free in sctp_epaddr_lookup_transport+0xacb/0xb20
> net/sctp/input.c:971
> Read of size 8 at addr ffff8881cde426b0 by task syz-executor3/18110
>
The same fix is needed in sctp_epaddr_lookup_transport() as:
commit bab1be79a5169ac748d8292b20c86d874022d7ba
Author: Xin Long <lucien.xin@...il.com>
Date:   Mon Aug 27 18:38:31 2018 +0800

    sctp: hold transport before accessing its asoc in sctp_transport_get_next

> CPU: 1 PID: 18110 Comm: syz-executor3 Not tainted 4.20.0-rc2+ #187
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x244/0x39d lib/dump_stack.c:113
>   print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
>   kasan_report_error mm/kasan/report.c:354 [inline]
>   kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
>   __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>   sctp_epaddr_lookup_transport+0xacb/0xb20 net/sctp/input.c:971
>   sctp_endpoint_lookup_assoc+0xe0/0x290 net/sctp/endpointola.c:338
>   sctp_addr_id2transport+0x1f8/0x370 net/sctp/socket.c:279
>   sctp_getsockopt_peer_addr_params+0x17c/0x1260 net/sctp/socket.c:5613
>   sctp_getsockopt+0x44f9/0x7d32 net/sctp/socket.c:7462
>   sock_common_getsockopt+0x9a/0xe0 net/core/sock.c:2937
>   __sys_getsockopt+0x1ad/0x390 net/socket.c:1939
>   __do_sys_getsockopt net/socket.c:1950 [inline]
>   __se_sys_getsockopt net/socket.c:1947 [inline]
>   __x64_sys_getsockopt+0xbe/0x150 net/socket.c:1947
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457569
> Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f177b561c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
> RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000457569
> RDX: 0000000000000009 RSI: 0000000000000084 RDI: 0000000000000006
> RBP: 000000000072c180 R08: 000000002044fffc R09: 0000000000000000
> R10: 0000000020a68000 R11: 0000000000000246 R12: 00007f177b5626d4
> R13: 00000000004c8318 R14: 00000000004ce200 R15: 00000000ffffffff
>
> Allocated by task 18068:
>   save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>   set_track mm/kasan/kasan.c:460 [inline]
>   kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
>   kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
>   kmalloc include/linux/slab.h:546 [inline]
>   kzalloc include/linux/slab.h:741 [inline]
>   sctp_association_new+0x14e/0x2290 net/sctp/associola.c:311
>   sctp_sendmsg_new_asoc+0x39c/0x11f0 net/sctp/socket.c:1723
>   sctp_sendmsg+0x18a5/0x1da0 net/sctp/socket.c:2086
>   inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
>   sock_sendmsg_nosec net/socket.c:621 [inline]
>   sock_sendmsg+0xd5/0x120 net/socket.c:631
>   __sys_sendto+0x3d7/0x670 net/socket.c:1788
>   __do_sys_sendto net/socket.c:1800 [inline]
>   __se_sys_sendto net/socket.c:1796 [inline]
>   __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1796
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 18110:
>   save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>   set_track mm/kasan/kasan.c:460 [inline]
>   __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
>   kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>   __cache_free mm/slab.c:3498 [inline]
>   kfree+0xcf/0x230 mm/slab.c:3817
>   sctp_association_destroy net/sctp/associola.c:437 [inline]
>   sctp_association_put+0x264/0x350 net/sctp/associola.c:889
>   sctp_transport_destroy net/sctp/transport.c:180 [inline]
>   sctp_transport_put+0x186/0x1f0 net/sctp/transport.c:340
>   sctp_hash_cmp+0x1ef/0x260 net/sctp/input.c:825
>   __rhashtable_lookup include/linux/rhashtable.h:483 [inline]
>   rhltable_lookup include/linux/rhashtable.h:566 [inline]
>   sctp_epaddr_lookup_transport+0x4fe/0xb20 net/sctp/input.c:967
>   sctp_endpoint_lookup_assoc+0xe0/0x290 net/sctp/endpointola.c:338
>   sctp_addr_id2transport+0x1f8/0x370 net/sctp/socket.c:279
>   sctp_getsockopt_peer_addr_params+0x17c/0x1260 net/sctp/socket.c:5613
>   sctp_getsockopt+0x44f9/0x7d32 net/sctp/socket.c:7462
>   sock_common_getsockopt+0x9a/0xe0 net/core/sock.c:2937
>   __sys_getsockopt+0x1ad/0x390 net/socket.c:1939
>   __do_sys_getsockopt net/socket.c:1950 [inline]
>   __se_sys_getsockopt net/socket.c:1947 [inline]
>   __x64_sys_getsockopt+0xbe/0x150 net/socket.c:1947
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff8881cde42600
>   which belongs to the cache kmalloc-4k of size 4096
> The buggy address is located 176 bytes inside of
>   4096-byte region [ffff8881cde42600, ffff8881cde43600)
> The buggy address belongs to the page:
> page:ffffea0007379080 count:1 mapcount:0 mapping:ffff8881da800dc0 index:0x0
> compound_mapcount: 0
> flags: 0x2fffc0000010200(slab|head)
> raw: 02fffc0000010200 ffffea0007379008 ffffea0007377f08 ffff8881da800dc0
> raw: 0000000000000000 ffff8881cde42600 0000000100000001 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8881cde42580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>   ffff8881cde42600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8881cde42680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                       ^
>   ffff8881cde42700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881cde42780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> kobject: 'loop5' (00000000f0e4ffac): fill_kobj_path: path
> = '/devices/virtual/block/loop5'
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

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