==================================================================
BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read-write to 0xffff8881078cfcc0 of 4 bytes by task 4081 on cpu 1:
 d_set_d_op+0xfb/0x1f0 fs/dcache.c:1799
 proc_pident_instantiate+0x164/0x180 fs/proc/base.c:2651
 proc_pident_lookup+0x112/0x180 fs/proc/base.c:2674
 proc_tgid_base_lookup+0x2b/0x40 fs/proc/base.c:3386
 __lookup_slow+0x184/0x250 fs/namei.c:1718
 lookup_slow+0x3c/0x60 fs/namei.c:1735
 walk_component fs/namei.c:2039 [inline]
 link_path_walk+0x69e/0x820 fs/namei.c:2404
 path_openat+0x1aa/0x1f10 fs/namei.c:3882
 do_filp_open+0xf7/0x200 fs/namei.c:3913
 do_sys_openat2+0xab/0x120 fs/open.c:1416
 do_sys_open fs/open.c:1431 [inline]
 __do_sys_openat fs/open.c:1447 [inline]
 __se_sys_openat fs/open.c:1442 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1442
 x64_sys_call+0x1025/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881078cfcc0 of 4 bytes by task 4080 on cpu 0:
 d_in_lookup include/linux/dcache.h:378 [inline]
 d_wait_lookup fs/dcache.c:2452 [inline]
 d_alloc_parallel+0x60b/0xc80 fs/dcache.c:2540
 __lookup_slow+0x8d/0x250 fs/namei.c:1703
 lookup_slow+0x3c/0x60 fs/namei.c:1735
 walk_component fs/namei.c:2039 [inline]
 link_path_walk+0x69e/0x820 fs/namei.c:2404
 path_openat+0x1aa/0x1f10 fs/namei.c:3882
 do_filp_open+0xf7/0x200 fs/namei.c:3913
 do_sys_openat2+0xab/0x120 fs/open.c:1416
 do_sys_open fs/open.c:1431 [inline]
 __do_sys_openat fs/open.c:1447 [inline]
 __se_sys_openat fs/open.c:1442 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1442
 x64_sys_call+0x1025/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x10000000 -> 0x1000000c

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4080 Comm: syz.0.159 Not tainted 6.11.0-rc2-syzkaller-00239-g34ac1e82e5a7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
==================================================================
loop0: detected capacity change from 0 to 1024
loop0: detected capacity change from 0 to 1024
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
syz.0.159: attempt to access beyond end of device
loop0: rw=12288, sector=32, nr_sectors = 2 limit=0
EXT4-fs error (device loop0): __ext4_find_entry:1641: inode #2: comm syz.0.159: reading directory lblock 0
syz.0.159: attempt to access beyond end of device
loop0: rw=145409, sector=2, nr_sectors = 2 limit=0
Buffer I/O error on dev loop0, logical block 1, lost sync page write
EXT4-fs (loop0): I/O error while writing superblock
syz.0.159: attempt to access beyond end of device
loop0: rw=12288, sector=32, nr_sectors = 2 limit=0
EXT4-fs error (device loop0): __ext4_find_entry:1641: inode #2: comm syz.0.159: reading directory lblock 0
syz.0.159: attempt to access beyond end of device
loop0: rw=145409, sector=2, nr_sectors = 2 limit=0
Buffer I/O error on dev loop0, logical block 1, lost sync page write
EXT4-fs (loop0): I/O error while writing superblock
syz.0.159: attempt to access beyond end of device
loop0: rw=12288, sector=32, nr_sectors = 2 limit=0
EXT4-fs error (device loop0): __ext4_find_entry:1641: inode #2: comm syz.0.159: reading directory lblock 0
syz.0.159: attempt to access beyond end of device
loop0: rw=145409, sector=2, nr_sectors = 2 limit=0
Buffer I/O error on dev loop0, logical block 1, lost sync page write
EXT4-fs (loop0): I/O error while writing superblock
EXT4-fs error (device loop0): ext4_get_inode_loc:4574: inode #2: block 5: comm syz.0.159: unable to read itable block
Buffer I/O error on dev loop0, logical block 1, lost sync page write
EXT4-fs (loop0): I/O error while writing superblock
EXT4-fs error (device loop0) in ext4_reserve_inode_write:5810: IO failure
Buffer I/O error on dev loop0, logical block 1, lost sync page write
EXT4-fs (loop0): I/O error while writing superblock
EXT4-fs error (device loop0): ext4_dirty_inode:6014: inode #2: comm syz.0.159: mark_inode_dirty error
EXT4-fs (loop0): previous I/O error to superblock detected
Buffer I/O error on dev loop0, logical block 1, lost sync page write