syzbot

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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read-write to 0xffff8881065ddb40 of 4 bytes by task 29117 on cpu 0:
 d_set_d_op+0xfb/0x1f0 fs/dcache.c:1804
 proc_pident_instantiate+0x164/0x180 fs/proc/base.c:2709
 proc_pident_lookup+0x112/0x190 fs/proc/base.c:2732
 proc_tgid_base_lookup+0x2b/0x40 fs/proc/base.c:3444
 __lookup_slow+0x184/0x250 fs/namei.c:1732
 lookup_slow+0x3c/0x60 fs/namei.c:1749
 walk_component fs/namei.c:2053 [inline]
 link_path_walk+0x69e/0x820 fs/namei.c:2418
 path_openat+0x1af/0x1fa0 fs/namei.c:3929
 do_filp_open+0xf7/0x200 fs/namei.c:3960
 do_sys_openat2+0xab/0x120 fs/open.c:1415
 do_sys_open fs/open.c:1430 [inline]
 __do_sys_openat fs/open.c:1446 [inline]
 __se_sys_openat fs/open.c:1441 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1441
 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 0xffff8881065ddb40 of 4 bytes by task 29116 on cpu 1:
 d_in_lookup include/linux/dcache.h:378 [inline]
 d_wait_lookup fs/dcache.c:2459 [inline]
 d_alloc_parallel+0x60b/0xc80 fs/dcache.c:2547
 __lookup_slow+0x8d/0x250 fs/namei.c:1717
 lookup_slow+0x3c/0x60 fs/namei.c:1749
 walk_component fs/namei.c:2053 [inline]
 link_path_walk+0x69e/0x820 fs/namei.c:2418
 path_openat+0x1af/0x1fa0 fs/namei.c:3929
 do_filp_open+0xf7/0x200 fs/namei.c:3960
 do_sys_openat2+0xab/0x120 fs/open.c:1415
 do_sys_open fs/open.c:1430 [inline]
 __do_sys_openat fs/open.c:1446 [inline]
 __se_sys_openat fs/open.c:1441 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1441
 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: 1 UID: 0 PID: 29116 Comm: syz.6.6699 Tainted: G        W          6.12.0-rc4-syzkaller-00261-g850925a8133c #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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