syzbot

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BUG: KCSAN: data-race in __alloc_file / init_peercred

write to 0xffff8880a650d2d8 of 4 bytes by task 14744 on cpu 0:
 get_cred include/linux/cred.h:253 [inline]
 __alloc_file+0x74/0x210 fs/file_table.c:105
 alloc_empty_file+0x8f/0x180 fs/file_table.c:151
 alloc_file+0x4e/0x2b0 fs/file_table.c:193
 alloc_file_pseudo+0x11c/0x1b0 fs/file_table.c:232
 __shmem_file_setup.part.0+0xd4/0x1f0 mm/shmem.c:4113
 __shmem_file_setup mm/shmem.c:4096 [inline]
 shmem_file_setup+0x7b/0xa0 mm/shmem.c:4143
 __do_sys_memfd_create mm/memfd.c:307 [inline]
 __se_sys_memfd_create mm/memfd.c:250 [inline]
 __x64_sys_memfd_create+0x20d/0x370 mm/memfd.c:250
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8880a650d2d8 of 4 bytes by task 14743 on cpu 1:
 get_cred include/linux/cred.h:253 [inline]
 init_peercred+0x108/0x150 net/unix/af_unix.c:595
 unix_socketpair+0x84/0x110 net/unix/af_unix.c:1398
 __sys_socketpair+0x227/0x450 net/socket.c:1586
 __do_sys_socketpair net/socket.c:1622 [inline]
 __se_sys_socketpair net/socket.c:1619 [inline]
 __x64_sys_socketpair+0x5e/0x80 net/socket.c:1619
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14743 Comm: syz-executor.3 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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