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BUG: KASAN: slab-out-of-bounds in sctp_send_reset_streams+0xb03/0xc10 net/sctp/stream.c:323
Read of size 2 at addr ffff8801d7f07a48 by task syz-executor1/6400

CPU: 1 PID: 6400 Comm: syz-executor1 Not tainted 4.15.0-rc2-next-20171208+ #63
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:428
 sctp_send_reset_streams+0xb03/0xc10 net/sctp/stream.c:323
 sctp_setsockopt_reset_streams net/sctp/socket.c:3905 [inline]
 sctp_setsockopt+0x70d/0x5d50 net/sctp/socket.c:4195
 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2968
 SYSC_setsockopt net/socket.c:1829 [inline]
 SyS_setsockopt+0x189/0x360 net/socket.c:1808
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452a39
RSP: 002b:00007f46bb9cfc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 0000000000452a39
RDX: 0000000000000077 RSI: 0000000000000084 RDI: 0000000000000016
RBP: 0000000000000079 R08: 0000000000000008 R09: 0000000000000000
R10: 0000000020e73ff8 R11: 0000000000000212 R12: 00000000006eebf8
R13: 00000000ffffffff R14: 00007f46bb9d06d4 R15: 0000000000000000

Allocated by task 6400:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 __do_kmalloc mm/slab.c:3712 [inline]
 __kmalloc_track_caller+0x15e/0x760 mm/slab.c:3727
 memdup_user+0x2c/0x90 mm/util.c:164
 sctp_setsockopt_reset_streams net/sctp/socket.c:3897 [inline]
 sctp_setsockopt+0x6a6/0x5d50 net/sctp/socket.c:4195
 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2968
 SYSC_setsockopt net/socket.c:1829 [inline]
 SyS_setsockopt+0x189/0x360 net/socket.c:1808
 entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 3377:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3492 [inline]
 kfree+0xca/0x250 mm/slab.c:3807
 simple_xattrs_free include/linux/xattr.h:97 [inline]
 shmem_evict_inode+0x1b0/0xb30 mm/shmem.c:1083
 evict+0x481/0x920 fs/inode.c:552
 iput_final fs/inode.c:1514 [inline]
 iput+0x7b9/0xaf0 fs/inode.c:1541
 dentry_unlink_inode+0x4b0/0x5e0 fs/dcache.c:376
 d_delete+0x1a7/0x250 fs/dcache.c:2367
 vfs_rmdir+0x32d/0x410 fs/namei.c:3889
 do_rmdir+0x4c8/0x5f0 fs/namei.c:3937
 SYSC_rmdir fs/namei.c:3955 [inline]
 SyS_rmdir+0x1a/0x20 fs/namei.c:3953
 entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff8801d7f07a40
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 8 bytes inside of
 32-byte region [ffff8801d7f07a40, ffff8801d7f07a60)
The buggy address belongs to the page:
page:000000000b3372a9 count:1 mapcount:0 mapping:00000000ae71d74a index:0xffff8801d7f07fc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d7f07000 ffff8801d7f07fc1 000000010000003f
raw: ffffea000718b220 ffffea00071732a0 ffff8801dac001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d7f07900: 00 00 00 fc fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8801d7f07980: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff8801d7f07a00: fb fb fb fb fc fc fc fc 00 fc fc fc fc fc fc fc
                                              ^
 ffff8801d7f07a80: 00 00 04 fc fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8801d7f07b00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
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