syzbot

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BUG: KCSAN: data-race in link_path_walk / shrink_dentry_list

write to 0xffff888132966cc0 of 4 bytes by task 15987 on cpu 0:
 shrink_dentry_list+0x127/0x340 fs/dcache.c:423
 shrink_dcache_sb+0x188/0x2d0 fs/dcache.c:1296
 reconfigure_super+0x2aa/0x4f0 fs/super.c:889
 do_remount fs/namespace.c:2653 [inline]
 path_mount+0x1442/0x1ce0 fs/namespace.c:3241
 do_mount fs/namespace.c:3262 [inline]
 __do_sys_mount fs/namespace.c:3470 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3447
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3447
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888132966cc0 of 4 bytes by task 15992 on cpu 1:
 link_path_walk+0x384/0x770 fs/namei.c:2248
 path_lookupat+0x8b/0x3d0 fs/namei.c:2437
 filename_lookup+0x118/0x3b0 fs/namei.c:2467
 kern_path+0x2e/0x40 fs/namei.c:2554
 do_loopback fs/namespace.c:2381 [inline]
 path_mount+0x468/0x1ce0 fs/namespace.c:3243
 do_mount fs/namespace.c:3262 [inline]
 __do_sys_mount fs/namespace.c:3470 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3447
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3447
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00280400 -> 0x00200000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15992 Comm: syz-executor.0 Not tainted 5.14.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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