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BUG: KCSAN: data-race in __d_instantiate / step_into

read-write to 0xffff8881004d1180 of 4 bytes by task 7818 on cpu 0:
 __d_instantiate+0x2cd/0x3c0 fs/dcache.c:1855
 d_instantiate_new+0x5c/0xf0 fs/dcache.c:1899
 ext4_add_nondir+0x16c/0x1a0 fs/ext4/namei.c:2797
 ext4_mknod+0x210/0x2f0 fs/ext4/namei.c:2872
 vfs_mknod+0x2d4/0x310 fs/namei.c:4009
 unix_bind_bsd net/unix/af_unix.c:1228 [inline]
 unix_bind+0x312/0x8a0 net/unix/af_unix.c:1319
 __sys_bind+0x15b/0x1d0 net/socket.c:1847
 __do_sys_bind net/socket.c:1858 [inline]
 __se_sys_bind net/socket.c:1856 [inline]
 __x64_sys_bind+0x41/0x50 net/socket.c:1856
 x64_sys_call+0x257d/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:50
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881004d1180 of 4 bytes by task 7819 on cpu 1:
 __follow_mount_rcu fs/namei.c:1485 [inline]
 handle_mounts fs/namei.c:1536 [inline]
 step_into+0xe7/0x810 fs/namei.c:1842
 walk_component+0x169/0x230 fs/namei.c:2010
 lookup_last fs/namei.c:2469 [inline]
 path_lookupat+0x10a/0x2b0 fs/namei.c:2493
 filename_lookup+0x127/0x300 fs/namei.c:2522
 kern_path+0x39/0x110 fs/namei.c:2630
 unix_find_bsd net/unix/af_unix.c:1064 [inline]
 unix_find_other+0x88/0x550 net/unix/af_unix.c:1125
 unix_dgram_connect+0x2c5/0x7f0 net/unix/af_unix.c:1379
 __sys_connect_file net/socket.c:2048 [inline]
 __sys_connect+0x1a9/0x1c0 net/socket.c:2065
 __do_sys_connect net/socket.c:2075 [inline]
 __se_sys_connect net/socket.c:2072 [inline]
 __x64_sys_connect+0x41/0x50 net/socket.c:2072
 x64_sys_call+0x2929/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:43
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00500000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7819 Comm: syz-executor.2 Not tainted 6.9.0-syzkaller-08414-g7ee332c9f12b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
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