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BUG: KASAN: double-free or invalid-free in relay_open+0x603/0x860 kernel/relay.c:614

CPU: 1 PID: 3335 Comm: syzkaller992317 Not tainted 4.9.72-gcb7518e #114
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801c9b57988 ffffffff81d922b9 ffffea0007200300 ffff8801c800c280
 ffff8801da001280 ffffffff8137ba63 0000000000000282 ffff8801c9b579c0
 ffffffff8153bab3 ffff8801c800c280 ffffffff8137ba63 ffff8801da001280
Call Trace:
 [<ffffffff81d922b9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d922b9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8153bab3>] print_address_description+0x73/0x280 mm/kasan/report.c:252
 [<ffffffff8153bd24>] kasan_report_double_free+0x64/0xa0 mm/kasan/report.c:333
 [<ffffffff8153b454>] kasan_slab_free+0xa4/0xc0 mm/kasan/kasan.c:572
 [<ffffffff81537fa3>] slab_free_hook mm/slub.c:1355 [inline]
 [<ffffffff81537fa3>] slab_free_freelist_hook mm/slub.c:1377 [inline]
 [<ffffffff81537fa3>] slab_free mm/slub.c:2958 [inline]
 [<ffffffff81537fa3>] kfree+0x103/0x300 mm/slub.c:3878
 [<ffffffff8137ba63>] relay_open+0x603/0x860 kernel/relay.c:614
 [<ffffffff813bd839>] do_blk_trace_setup+0x3e9/0x950 kernel/trace/blktrace.c:501
 [<ffffffff813bde80>] blk_trace_setup+0xe0/0x1a0 kernel/trace/blktrace.c:545
 [<ffffffff8266e770>] sg_ioctl+0xbe0/0x2c30 drivers/scsi/sg.c:1099
 [<ffffffff815abdda>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815abdda>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815acdff>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815acdff>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838af585>] entry_SYSCALL_64_fastpath+0x23/0xc6

Allocated by task 3335:
 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
 sg_ioctl+0xbe0/0x2c30 drivers/scsi/sg.c:1099
 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+0x23/0xc6

Freed by task 3335:
 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
 sg_ioctl+0xbe0/0x2c30 drivers/scsi/sg.c:1099
 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+0x23/0xc6

The buggy address belongs to the object at ffff8801c800c280
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8801c800c280, ffff8801c800c480)
The buggy address belongs to the page:
page:ffffea0007200300 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:
 ffff8801c800c180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c800c200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c800c280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8801c800c300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c800c380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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