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BUG: KASAN: use-after-free in ucma_close+0x2a4/0x310 drivers/infiniband/core/ucma.c:1839
Read of size 4 at addr ffff8880a748b538 by task syz-executor.0/7260

CPU: 0 PID: 7260 Comm: syz-executor.0 Not tainted 5.9.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 ucma_close+0x2a4/0x310 drivers/infiniband/core/ucma.c:1839
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:141
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:163 [inline]
 exit_to_user_mode_prepare+0x1e1/0x200 kernel/entry/common.c:190
 syscall_exit_to_user_mode+0x7e/0x2e0 kernel/entry/common.c:265
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x416f01
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffd5e376f90 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000416f01
RDX: 0000000000000001 RSI: 0000000000000080 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 00007ffd5e377080 R11: 0000000000000293 R12: 0000000001190ed0
R13: 000000000007fa65 R14: ffffffffffffffff R15: 000000000118cfec

Allocated by task 7261:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 kmem_cache_alloc_trace+0x174/0x2c0 mm/slab.c:3550
 kmalloc include/linux/slab.h:554 [inline]
 kzalloc include/linux/slab.h:666 [inline]
 ucma_alloc_ctx+0x4b/0x480 drivers/infiniband/core/ucma.c:212
 ucma_create_id+0x11b/0x590 drivers/infiniband/core/ucma.c:502
 ucma_write+0x288/0x350 drivers/infiniband/core/ucma.c:1768
 vfs_write+0x2b0/0x730 fs/read_write.c:576
 ksys_write+0x1ee/0x250 fs/read_write.c:631
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 7261:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
 __cache_free mm/slab.c:3418 [inline]
 kfree+0x10e/0x2b0 mm/slab.c:3756
 ucma_free_ctx+0x7f6/0xae0 drivers/infiniband/core/ucma.c:600
 ucma_destroy_id+0x30c/0x460 drivers/infiniband/core/ucma.c:644
 ucma_write+0x288/0x350 drivers/infiniband/core/ucma.c:1768
 vfs_write+0x2b0/0x730 fs/read_write.c:576
 ksys_write+0x1ee/0x250 fs/read_write.c:631
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8880a748b400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 312 bytes inside of
 512-byte region [ffff8880a748b400, ffff8880a748b600)
The buggy address belongs to the page:
page:000000002b52c09c refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xa748b
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002416c48 ffff8880aa041750 ffff8880aa040600
raw: 0000000000000000 ffff8880a748b000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a748b400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a748b480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a748b500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff8880a748b580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a748b600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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