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BUG: KCSAN: data-race in __d_instantiate / step_into

read-write to 0xffff888135e99f00 of 4 bytes by task 14411 on cpu 0:
 __d_instantiate+0x2cd/0x3c0 fs/dcache.c:1855
 d_instantiate_new+0x5c/0xf0 fs/dcache.c:1899
 ext4_add_nondir+0x16c/0x190 fs/ext4/namei.c:2798
 ext4_create+0x20e/0x2f0 fs/ext4/namei.c:2839
 vfs_create+0x194/0x280 fs/namei.c:3198
 do_mknodat+0x2a4/0x420 fs/namei.c:4050
 __do_sys_mknodat fs/namei.c:4078 [inline]
 __se_sys_mknodat fs/namei.c:4075 [inline]
 __x64_sys_mknodat+0x62/0x70 fs/namei.c:4075
 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+0x63/0x6b

read to 0xffff888135e99f00 of 4 bytes by task 14410 on cpu 1:
 __follow_mount_rcu fs/namei.c:1486 [inline]
 handle_mounts fs/namei.c:1537 [inline]
 step_into+0xe7/0x800 fs/namei.c:1839
 walk_component+0x164/0x230 fs/namei.c:2007
 lookup_last fs/namei.c:2458 [inline]
 path_lookupat+0x10a/0x2a0 fs/namei.c:2482
 filename_lookup+0x126/0x300 fs/namei.c:2511
 user_path_at_empty+0x42/0x120 fs/namei.c:2920
 user_path_at include/linux/namei.h:57 [inline]
 path_setxattr+0x60/0x1a0 fs/xattr.c:667
 __do_sys_lsetxattr fs/xattr.c:695 [inline]
 __se_sys_lsetxattr fs/xattr.c:691 [inline]
 __x64_sys_lsetxattr+0x6a/0x80 fs/xattr.c:691
 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+0x63/0x6b

value changed: 0x00080000 -> 0x00480040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14410 Comm: syz-executor.2 Tainted: G        W          6.8.0-rc4-syzkaller-00410-gc02197fc9076 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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