Date:   Mon, 23 Apr 2018 14:56:35 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     syzbot <syzbot+cd494c1dd681d4d93ebb@...kaller.appspotmail.com>
Cc:     davem <davem@...emloft.net>, LKML <linux-kernel@...r.kernel.org>,
        linux-sctp@...r.kernel.org, network dev <netdev@...r.kernel.org>,
        Neil Horman <nhorman@...driver.com>,
        syzkaller-bugs@...glegroups.com,
        Vlad Yasevich <vyasevich@...il.com>
Subject: Re: KASAN: slab-out-of-bounds Read in __sctp_v6_cmp_addr

On Mon, Apr 23, 2018 at 9:02 AM, syzbot
<syzbot+cd494c1dd681d4d93ebb@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on upstream commit
> 83beed7b2b26f232d782127792dd0cd4362fdc41 (Fri Apr 20 17:56:32 2018 +0000)
> Merge branch 'fixes' of
> git://git.kernel.org/pub/scm/linux/kernel/git/evalenti/linux-soc-thermal
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=cd494c1dd681d4d93ebb
>
> So far this crash happened 305 times on net-next, upstream.
> C reproducer: https://syzkaller.appspot.com/x/repro.c?id=6684817483628544
> syzkaller reproducer:
> https://syzkaller.appspot.com/x/repro.syz?id=6321732692475904
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=5381423422767104
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=1808800213120130118
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+cd494c1dd681d4d93ebb@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in ipv6_addr_equal include/net/ipv6.h:507
> [inline]
> BUG: KASAN: slab-out-of-bounds in __sctp_v6_cmp_addr+0x4c7/0x530
> net/sctp/ipv6.c:580
Two v4 addresses went into ipv6_addr_equal, this happens when one
v4 socket bind v4 addr A, then another v6 socket tries to bind the
same v4 addr A.

This is an old issue, I will send a fix soon. Thanks.

> Read of size 8 at addr ffff8801b58626d0 by task syzkaller106428/4452
>
> CPU: 1 PID: 4452 Comm: syzkaller106428 Not tainted 4.17.0-rc1+ #10
> 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+0x1b9/0x294 lib/dump_stack.c:113
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>  ipv6_addr_equal include/net/ipv6.h:507 [inline]
>  __sctp_v6_cmp_addr+0x4c7/0x530 net/sctp/ipv6.c:580
>  sctp_inet6_cmp_addr+0x169/0x1a0 net/sctp/ipv6.c:898
>  sctp_bind_addr_conflict+0x28c/0x470 net/sctp/bind_addr.c:368
>  sctp_get_port_local+0x9fc/0x1540 net/sctp/socket.c:7515
>  sctp_do_bind+0x21c/0x5f0 net/sctp/socket.c:435
>  sctp_bindx_add+0x90/0x1a0 net/sctp/socket.c:529
>  sctp_setsockopt_bindx+0x2ad/0x320 net/sctp/socket.c:1058
>  sctp_setsockopt+0x12c4/0x7000 net/sctp/socket.c:4227
>  sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3039
>  __sys_setsockopt+0x1bd/0x390 net/socket.c:1903
>  __do_sys_setsockopt net/socket.c:1914 [inline]
>  __se_sys_setsockopt net/socket.c:1911 [inline]
>  __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1911
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x445839
> RSP: 002b:00007fbe3f0fdd98 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 00000000006dac24 RCX: 0000000000445839
> RDX: 0000000000000064 RSI: 0000000000000084 RDI: 0000000000000004
> RBP: 00000000006dac20 R08: 0000000000000010 R09: 000000000000a6fe
> R10: 00000000205ba000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffc1404827f R14: 00007fbe3f0fe9c0 R15: 0000000000000003
>
> Allocated by task 4452:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
>  __do_kmalloc_node mm/slab.c:3682 [inline]
>  __kmalloc_node+0x47/0x70 mm/slab.c:3689
>  kmalloc_node include/linux/slab.h:554 [inline]
>  kvmalloc_node+0x6b/0x100 mm/util.c:421
>  kvmalloc include/linux/mm.h:550 [inline]
>  vmemdup_user+0x2d/0xa0 mm/util.c:186
>  sctp_setsockopt_bindx+0x5d/0x320 net/sctp/socket.c:1022
>  sctp_setsockopt+0x12c4/0x7000 net/sctp/socket.c:4227
>  sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3039
>  __sys_setsockopt+0x1bd/0x390 net/socket.c:1903
>  __do_sys_setsockopt net/socket.c:1914 [inline]
>  __se_sys_setsockopt net/socket.c:1911 [inline]
>  __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1911
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 2818:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
>  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>  __cache_free mm/slab.c:3498 [inline]
>  kfree+0xd9/0x260 mm/slab.c:3813
>  single_release+0x8f/0xb0 fs/seq_file.c:609
>  __fput+0x34d/0x890 fs/file_table.c:209
>  ____fput+0x15/0x20 fs/file_table.c:243
>  task_work_run+0x1e4/0x290 kernel/task_work.c:113
>  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
>  exit_to_usermode_loop+0x2bd/0x310 arch/x86/entry/common.c:166
>  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
>  do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff8801b58626c0
>  which belongs to the cache kmalloc-32 of size 32
> The buggy address is located 16 bytes inside of
>  32-byte region [ffff8801b58626c0, ffff8801b58626e0)
> The buggy address belongs to the page:
> page:ffffea0006d61880 count:1 mapcount:0 mapping:ffff8801b5862000
> index:0xffff8801b5862fc1
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801b5862000 ffff8801b5862fc1 0000000100000032
> raw: ffffea0006ddd1e0 ffffea0006dd2860 ffff8801da8001c0 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801b5862580: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>  ffff8801b5862600: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>>
>> ffff8801b5862680: fb fb fb fb fc fc fc fc 00 00 fc fc fc fc fc fc
>
>                                                  ^
>  ffff8801b5862700: 00 00 00 00 fc fc fc fc 00 00 04 fc fc fc fc fc
>  ffff8801b5862780: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
> ==================================================================
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
> into any tree, please reply to this email with:
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