memory leak in rw_copy_check

Patch testing requests:
Created	Duration	User	Patch	Repo	Result
2020/10/15 22:19	16m	anant.thazhemadam@gmail.com		upstream	OK
2020/08/24 16:50	7m	anmol.karan123@gmail.com		upstream	report log

BUG: memory leak
unreferenced object 0xffff88811c405400 (size 1024):
  comm "syz-executor386", pid 6503, jiffies 4294942347 (age 13.130s)
  hex dump (first 32 bytes):
    00 01 00 20 00 00 00 00 14 00 00 00 00 00 00 00  ... ............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<000000001a62dd57>] kmalloc_array include/linux/slab.h:594 [inline]
    [<000000001a62dd57>] rw_copy_check_uvector+0x171/0x1a0 fs/read_write.c:812
    [<0000000016ad020b>] import_iovec+0x4a/0x140 lib/iov_iter.c:1681
    [<00000000fb58399a>] io_import_iovec+0x271/0x640 fs/io_uring.c:2879
    [<0000000002d03b50>] io_rw_prep_async fs/io_uring.c:3006 [inline]
    [<0000000002d03b50>] io_read_prep+0x94/0xf0 fs/io_uring.c:3031
    [<000000008ab01d5d>] io_req_defer_prep fs/io_uring.c:5462 [inline]
    [<000000008ab01d5d>] io_req_defer_prep+0x1c6/0x720 fs/io_uring.c:5442
    [<0000000075ed8a70>] io_submit_sqe fs/io_uring.c:6262 [inline]
    [<0000000075ed8a70>] io_submit_sqes+0x306/0xc00 fs/io_uring.c:6488
    [<00000000d1d617da>] __do_sys_io_uring_enter+0x582/0x830 fs/io_uring.c:8265
    [<00000000334cee0e>] do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
    [<0000000053cdb89f>] entry_SYSCALL_64_after_hwframe+0x44/0xa9