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BUG: KASAN: use-after-free in ucma_close+0x2d7/0x2f0 drivers/infiniband/core/ucma.c:1693
Read of size 8 at addr ffff8801bafea3c0 by task syz-executor0/8431

CPU: 0 PID: 8431 Comm: syz-executor0 Not tainted 4.16.0-rc5+ #352
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+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 ucma_close+0x2d7/0x2f0 drivers/infiniband/core/ucma.c:1693
 __fput+0x327/0x7e0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x199/0x270 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x275/0x2f0 arch/x86/entry/common.c:166
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
 do_syscall_64+0x6ec/0x940 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453e69
RSP: 002b:00007f4efe4d0c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000124
RAX: 0000000000000014 RBX: 00007f4efe4d16d4 RCX: 0000000000453e69
RDX: 0000000000000000 RSI: 0000000000000014 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000006d R14: 00000000006f0ad8 R15: 0000000000000000

Allocated by task 8431:
 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:552
 kmem_cache_alloc_trace+0x136/0x740 mm/slab.c:3607
 kmalloc include/linux/slab.h:512 [inline]
 kzalloc include/linux/slab.h:701 [inline]
 ucma_alloc_ctx+0xce/0x610 drivers/infiniband/core/ucma.c:188
 ucma_create_id+0x205/0x620 drivers/infiniband/core/ucma.c:473
 ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1633
 __vfs_write+0xef/0x970 fs/read_write.c:480
 vfs_write+0x189/0x510 fs/read_write.c:544
 SYSC_write fs/read_write.c:589 [inline]
 SyS_write+0xef/0x220 fs/read_write.c:581
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 8431:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3485 [inline]
 kfree+0xd9/0x260 mm/slab.c:3800
 ucma_create_id+0x45b/0x620 drivers/infiniband/core/ucma.c:500
 ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1633
 __vfs_write+0xef/0x970 fs/read_write.c:480
 vfs_write+0x189/0x510 fs/read_write.c:544
 SYSC_write fs/read_write.c:589 [inline]
 SyS_write+0xef/0x220 fs/read_write.c:581
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801bafea340
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 128 bytes inside of
 256-byte region [ffff8801bafea340, ffff8801bafea440)
The buggy address belongs to the page:
page:ffffea0006ebfa80 count:1 mapcount:0 mapping:ffff8801bafea0c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bafea0c0 0000000000000000 000000010000000c
raw: ffffea0006c5ae20 ffffea0006cf1260 ffff8801dac007c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bafea280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc
 ffff8801bafea300: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff8801bafea380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff8801bafea400: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff8801bafea480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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