BUG: KASAN: double-free or invalid-free in relay_open+0x6a1/0xa40 kernel/relay.c:614

CPU: 0 PID: 3002 Comm: syzkaller677549 Not tainted 4.14.0-rc7-next-20171103+ #38
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_double_free+0x55/0x80 mm/kasan/report.c:333
 kasan_slab_free+0xa3/0xc0 mm/kasan/kasan.c:514
 __cache_free mm/slab.c:3493 [inline]
 kfree+0xca/0x250 mm/slab.c:3808
 relay_open+0x6a1/0xa40 kernel/relay.c:614
 do_blk_trace_setup+0x4a4/0xcf0 kernel/trace/blktrace.c:517
 blk_trace_setup+0xbd/0x180 kernel/trace/blktrace.c:564
 sg_ioctl+0xc77/0x2da0 drivers/scsi/sg.c:1089
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x444339
RSP: 002b:00007ffe35171878 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006d66c0 RCX: 0000000000444339
RDX: 000000002084cf90 RSI: 00000000c0481273 RDI: 0000000000000014
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: ffffffffffffffff
R13: 6000020000001276 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3002:
 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
 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3615
 kmalloc include/linux/slab.h:500 [inline]
 kzalloc include/linux/slab.h:689 [inline]
 relay_open+0xf2/0xa40 kernel/relay.c:576
 do_blk_trace_setup+0x4a4/0xcf0 kernel/trace/blktrace.c:517
 blk_trace_setup+0xbd/0x180 kernel/trace/blktrace.c:564
 sg_ioctl+0xc77/0x2da0 drivers/scsi/sg.c:1089
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 3002:
 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:3493 [inline]
 kfree+0xca/0x250 mm/slab.c:3808
 relay_destroy_channel kernel/relay.c:199 [inline]
 kref_put include/linux/kref.h:70 [inline]
 relay_open+0x84a/0xa40 kernel/relay.c:612
 do_blk_trace_setup+0x4a4/0xcf0 kernel/trace/blktrace.c:517
 blk_trace_setup+0xbd/0x180 kernel/trace/blktrace.c:564
 sg_ioctl+0xc77/0x2da0 drivers/scsi/sg.c:1089
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x1f/0xbe

The buggy address belongs to the object at ffff8801cf5a9840
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8801cf5a9840, ffff8801cf5a9a40)
The buggy address belongs to the page:
page:ffffea00073d6a40 count:1 mapcount:0 mapping:ffff8801cf5a90c0 index:0x0
flags: 0x200000000000100(slab)
raw: 0200000000000100 ffff8801cf5a90c0 0000000000000000 0000000100000006
raw: ffffea000739c1a0 ffffea00073adf20 ffff8801dac00940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cf5a9700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cf5a9780: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8801cf5a9800: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                           ^
 ffff8801cf5a9880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cf5a9900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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