syzbot

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BUG: KCSAN: data-race in link_path_walk / shrink_dentry_list

write to 0xffff888135267cc0 of 4 bytes by task 817 on cpu 0:
 shrink_dentry_list+0x127/0x540 fs/dcache.c:448
 shrink_dcache_sb+0x188/0x2d0 fs/dcache.c:1321
 reconfigure_super+0x146/0x540 fs/super.c:888
 do_remount fs/namespace.c:2656 [inline]
 path_mount+0x13f9/0x1c40 fs/namespace.c:3316
 do_mount fs/namespace.c:3337 [inline]
 __do_sys_mount fs/namespace.c:3545 [inline]
 __se_sys_mount+0x24b/0x2f0 fs/namespace.c:3522
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3522
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888135267cc0 of 4 bytes by task 815 on cpu 1:
 link_path_walk+0x409/0x990 fs/namei.c:2309
 path_lookupat+0x8b/0x3d0 fs/namei.c:2498
 filename_lookup+0x130/0x310 fs/namei.c:2528
 user_path_at_empty+0x3e/0x110 fs/namei.c:2851
 user_path_at include/linux/namei.h:57 [inline]
 do_mount fs/namespace.c:3334 [inline]
 __do_sys_mount fs/namespace.c:3545 [inline]
 __se_sys_mount+0x217/0x2f0 fs/namespace.c:3522
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3522
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00280440 -> 0x00200040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 815 Comm: syz-executor.0 Not tainted 5.17.0-rc2-syzkaller-00316-g0457e5153e0e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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