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

CPU: 1 PID: 7877 Comm: syz-executor1 Not tainted 4.15.0+ #296
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:3485 [inline]
 kfree+0xd6/0x260 mm/slab.c:3800
 relay_open+0x6a1/0xa40 kernel/relay.c:614
 do_blk_trace_setup+0x4a4/0xcd0 kernel/trace/blktrace.c:544
 __blk_trace_setup+0xbe/0x150 kernel/trace/blktrace.c:589
 blk_trace_ioctl+0x206/0x2e0 kernel/trace/blktrace.c:728
 blkdev_ioctl+0x1845/0x1e00 block/ioctl.c:587
 block_ioctl+0xde/0x120 fs/block_dev.c:1860
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x453299
RSP: 002b:00007fc31ac3fc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000453299
RDX: 0000000020f58000 RSI: 00000000c0481273 RDI: 0000000000000013
RBP: 0000000000000622 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f83d0
R13: 00000000ffffffff R14: 00007fc31ac406d4 R15: 0000000000000000

Allocated by task 7877:
 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:3607
 kmalloc include/linux/slab.h:512 [inline]
 kzalloc include/linux/slab.h:701 [inline]
 relay_open+0xf2/0xa40 kernel/relay.c:576
 do_blk_trace_setup+0x4a4/0xcd0 kernel/trace/blktrace.c:544
 __blk_trace_setup+0xbe/0x150 kernel/trace/blktrace.c:589
 blk_trace_ioctl+0x206/0x2e0 kernel/trace/blktrace.c:728
 blkdev_ioctl+0x1845/0x1e00 block/ioctl.c:587
 block_ioctl+0xde/0x120 fs/block_dev.c:1860
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 7877:
 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:3485 [inline]
 kfree+0xd6/0x260 mm/slab.c:3800
 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+0x4a4/0xcd0 kernel/trace/blktrace.c:544
 __blk_trace_setup+0xbe/0x150 kernel/trace/blktrace.c:589
 blk_trace_ioctl+0x206/0x2e0 kernel/trace/blktrace.c:728
 blkdev_ioctl+0x1845/0x1e00 block/ioctl.c:587
 block_ioctl+0xde/0x120 fs/block_dev.c:1860
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x29/0xa0

The buggy address belongs to the object at ffff8801bf3735c0
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8801bf3735c0, ffff8801bf3737c0)
The buggy address belongs to the page:
page:ffffea0006fcdcc0 count:1 mapcount:0 mapping:ffff8801bf3730c0 index:0xffff8801bf373840
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bf3730c0 ffff8801bf373840 0000000100000005
raw: ffffea0006f31f60 ffffea0006fcde20 ffff8801db000940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bf373480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bf373500: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8801bf373580: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                           ^
 ffff8801bf373600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bf373680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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