syzbot

==================================================================
BUG: KCSAN: data-race in vfs_readlink / vfs_readlink

write to 0xffff888120796082 of 2 bytes by task 15602 on cpu 1:
 vfs_readlink+0x20b/0x260 fs/namei.c:4539
 do_readlinkat+0x170/0x200 fs/stat.c:431
 __do_sys_readlinkat fs/stat.c:446 [inline]
 __se_sys_readlinkat fs/stat.c:443 [inline]
 __x64_sys_readlinkat+0x4f/0x60 fs/stat.c:443
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888120796082 of 2 bytes by task 15604 on cpu 0:
 vfs_readlink+0x56/0x260 fs/namei.c:4531
 do_readlinkat+0x170/0x200 fs/stat.c:431
 __do_sys_readlinkat fs/stat.c:446 [inline]
 __se_sys_readlinkat fs/stat.c:443 [inline]
 __x64_sys_readlinkat+0x4f/0x60 fs/stat.c:443
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 15604 Comm: systemd-udevd Not tainted 5.8.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 15604 Comm: systemd-udevd Not tainted 5.8.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x10f/0x19d lib/dump_stack.c:118
 panic+0x207/0x64a kernel/panic.c:231
 kcsan_report+0x684/0x690 kernel/kcsan/report.c:626
 kcsan_setup_watchpoint+0x453/0x4d0 kernel/kcsan/core.c:519
 vfs_readlink+0x56/0x260 fs/namei.c:4531
 do_readlinkat+0x170/0x200 fs/stat.c:431
 __do_sys_readlinkat fs/stat.c:446 [inline]
 __se_sys_readlinkat fs/stat.c:443 [inline]
 __x64_sys_readlinkat+0x4f/0x60 fs/stat.c:443
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f48a49710ba
Code: Bad RIP value.
RSP: 002b:00007ffe2b2abce8 EFLAGS: 00000206 ORIG_RAX: 000000000000010b
RAX: ffffffffffffffda RBX: 000055a339388100 RCX: 00007f48a49710ba
RDX: 000055a339388100 RSI: 00007ffe2b2abd70 RDI: 00000000ffffff9c
RBP: 0000000000000064 R08: 0000000000000000 R09: 0000000000000070
R10: 0000000000000063 R11: 0000000000000206 R12: 00007ffe2b2abd70
R13: 00000000ffffff9c R14: 00007ffe2b2abd40 R15: 0000000000000063
Kernel Offset: disabled
Rebooting in 86400 seconds..