audit: type=1400 audit(1517060941.764:12): avc:  denied  { net_raw } for  pid=4493 comm="syz-executor0" capability=13  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
BUG: KASAN: double-free or invalid-free in relay_open+0x603/0x860 kernel/relay.c:614

CPU: 0 PID: 4497 Comm: syz-executor1 Not tainted 4.9.78-g68d447c #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d01b78b8 ffffffff81d943a9 ffffea000742b800 ffff8801d0ae0500
 ffff8801da001280 ffffffff8137d7c3 0000000000000282 ffff8801d01b78f0
 ffffffff8153dc23 ffff8801d0ae0500 ffffffff8137d7c3 ffff8801da001280
Call Trace:
 [<ffffffff81d943a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d943a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8153dc23>] print_address_description+0x73/0x280 mm/kasan/report.c:252
 [<ffffffff8153de94>] kasan_report_double_free+0x64/0xa0 mm/kasan/report.c:333
 [<ffffffff8153d5c4>] kasan_slab_free+0xa4/0xc0 mm/kasan/kasan.c:572
 [<ffffffff8153a113>] slab_free_hook mm/slub.c:1355 [inline]
 [<ffffffff8153a113>] slab_free_freelist_hook mm/slub.c:1377 [inline]
 [<ffffffff8153a113>] slab_free mm/slub.c:2958 [inline]
 [<ffffffff8153a113>] kfree+0x103/0x300 mm/slub.c:3878
 [<ffffffff8137d7c3>] relay_open+0x603/0x860 kernel/relay.c:614
 [<ffffffff813bf529>] do_blk_trace_setup+0x3e9/0x950 kernel/trace/blktrace.c:501
 [<ffffffff813bfb70>] blk_trace_setup+0xe0/0x1a0 kernel/trace/blktrace.c:545
 [<ffffffff813c005e>] blk_trace_ioctl+0x1de/0x300 kernel/trace/blktrace.c:654
 [<ffffffff81d37b50>] blkdev_ioctl+0xb00/0x1a60 block/ioctl.c:576
 [<ffffffff8162be8e>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815adfaa>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815adfaa>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815aefcf>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815aefcf>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838b2c6e>] entry_SYSCALL_64_fastpath+0x29/0xe8

Allocated by task 4497:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:609
 kmem_cache_alloc_trace+0xfb/0x2a0 mm/slub.c:2742
 kmalloc include/linux/slab.h:490 [inline]
 kzalloc include/linux/slab.h:636 [inline]
 relay_open+0x91/0x860 kernel/relay.c:576
 do_blk_trace_setup+0x3e9/0x950 kernel/trace/blktrace.c:501
 blk_trace_setup+0xe0/0x1a0 kernel/trace/blktrace.c:545
 blk_trace_ioctl+0x1de/0x300 kernel/trace/blktrace.c:654
 blkdev_ioctl+0xb00/0x1a60 block/ioctl.c:576
 block_ioctl+0xde/0x120 fs/block_dev.c:1688
 vfs_ioctl fs/ioctl.c:43 [inline]
 do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 SYSC_ioctl fs/ioctl.c:694 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 entry_SYSCALL_64_fastpath+0x29/0xe8

Freed by task 4497:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582
 slab_free_hook mm/slub.c:1355 [inline]
 slab_free_freelist_hook mm/slub.c:1377 [inline]
 slab_free mm/slub.c:2958 [inline]
 kfree+0x103/0x300 mm/slub.c:3878
 relay_destroy_channel+0x16/0x20 kernel/relay.c:199
 kref_sub include/linux/kref.h:73 [inline]
 kref_put include/linux/kref.h:98 [inline]
 relay_open+0x5ea/0x860 kernel/relay.c:612
 do_blk_trace_setup+0x3e9/0x950 kernel/trace/blktrace.c:501
 blk_trace_setup+0xe0/0x1a0 kernel/trace/blktrace.c:545
 blk_trace_ioctl+0x1de/0x300 kernel/trace/blktrace.c:654
 blkdev_ioctl+0xb00/0x1a60 block/ioctl.c:576
 block_ioctl+0xde/0x120 fs/block_dev.c:1688
 vfs_ioctl fs/ioctl.c:43 [inline]
 do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 SYSC_ioctl fs/ioctl.c:694 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 entry_SYSCALL_64_fastpath+0x29/0xe8

The buggy address belongs to the object at ffff8801d0ae0500
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8801d0ae0500, ffff8801d0ae0700)
The buggy address belongs to the page:
page:ffffea000742b800 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x8000000000004080(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d0ae0400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d0ae0480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801d0ae0500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8801d0ae0580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d0ae0600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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