syzbot

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BUG: KCSAN: data-race in lookup_fast / shrink_dentry_list

read-write to 0xffff8881391700c0 of 4 bytes by task 6670 on cpu 1:
 d_shrink_del fs/dcache.c:448 [inline]
 shrink_dentry_list+0x16f/0x380 fs/dcache.c:1197
 prune_dcache_sb+0x72/0xa0 fs/dcache.c:1282
 super_cache_scan+0x24e/0x300 fs/super.c:104
 do_shrink_slab+0x2ad/0x600 mm/vmscan.c:770
 shrink_slab_memcg+0x1b9/0x440 mm/vmscan.c:839
 shrink_slab+0x5c/0x1c0 mm/vmscan.c:918
 shrink_node_memcgs+0x27a/0x400 mm/vmscan.c:3124
 shrink_node+0x8c3/0x10f0 mm/vmscan.c:3245
 shrink_zones+0x2c1/0x5d0 mm/vmscan.c:3482
 do_try_to_free_pages+0x165/0x720 mm/vmscan.c:3540
 try_to_free_mem_cgroup_pages+0x1cd/0x420 mm/vmscan.c:3854
 reclaim_high+0xcd/0x110 mm/memcontrol.c:2333
 mem_cgroup_handle_over_high+0x75/0x120 mm/memcontrol.c:2517
 resume_user_mode_work include/linux/resume_user_mode.h:58 [inline]
 exit_to_user_mode_loop+0xa5/0x130 kernel/entry/common.c:169
 exit_to_user_mode_prepare kernel/entry/common.c:201 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x6a/0x90 kernel/entry/common.c:294
 do_syscall_64+0x37/0x70 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881391700c0 of 4 bytes by task 6671 on cpu 0:
 d_revalidate fs/namei.c:847 [inline]
 lookup_fast+0x172/0x360 fs/namei.c:1650
 walk_component+0x6b/0x280 fs/namei.c:2010
 lookup_last fs/namei.c:2469 [inline]
 path_lookupat+0x11d/0x2b0 fs/namei.c:2493
 filename_lookup+0x130/0x310 fs/namei.c:2522
 user_path_at_empty+0x3e/0x110 fs/namei.c:2895
 user_path_at include/linux/namei.h:57 [inline]
 __do_sys_chdir fs/open.c:514 [inline]
 __se_sys_chdir+0x56/0x150 fs/open.c:508
 __x64_sys_chdir+0x1b/0x20 fs/open.c:508
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00080400 -> 0x00008000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6671 Comm: syz-executor.5 Not tainted 5.19.0-rc6-syzkaller-00115-g4a57a8400075-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
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