KASAN: slab-out-of-bounds Read in __sctp_v6_cmp_addr

From: syzbot
Date: Sun Apr 22 2018 - 21:02:32 EST

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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@xxxxxxxxxxxxxxxxxxxxxxxxx
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==================================================================
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
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
==================================================================

---
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Next in thread: Xin Long: "Re: KASAN: slab-out-of-bounds Read in __sctp_v6_cmp_addr"
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