==================================================================
BUG: KCSAN: data-race in copy_process / free_pid

write to 0xffffffff85a7b9b0 of 4 bytes by task 12706 on cpu 1:
 free_pid+0xf1/0x1b0 kernel/pid.c:134
 copy_process+0x316f/0x3b10 kernel/fork.c:2319
 _do_fork+0xf7/0x790 kernel/fork.c:2436
 __do_sys_clone kernel/fork.c:2591 [inline]
 __se_sys_clone kernel/fork.c:2572 [inline]
 __x64_sys_clone+0x12e/0x170 kernel/fork.c:2572
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffffff85a7b9b0 of 4 bytes by task 27939 on cpu 0:
 copy_process+0x27d8/0x3b10 kernel/fork.c:2233
 _do_fork+0xf7/0x790 kernel/fork.c:2436
 __do_sys_clone kernel/fork.c:2591 [inline]
 __se_sys_clone kernel/fork.c:2572 [inline]
 __x64_sys_clone+0x12e/0x170 kernel/fork.c:2572
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 27939 Comm: udevd Not tainted 5.6.0-rc1-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: 27939 Comm: udevd Not tainted 5.6.0-rc1-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+0x11d/0x187 lib/dump_stack.c:118
 panic+0x210/0x640 kernel/panic.c:221
 kcsan_report.cold+0xc/0x14 kernel/kcsan/report.c:609
 kcsan_setup_watchpoint+0x3e3/0x420 kernel/kcsan/core.c:503
 copy_process+0x27d8/0x3b10 kernel/fork.c:2233
 _do_fork+0xf7/0x790 kernel/fork.c:2436
 __do_sys_clone kernel/fork.c:2591 [inline]
 __se_sys_clone kernel/fork.c:2572 [inline]
 __x64_sys_clone+0x12e/0x170 kernel/fork.c:2572
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f8acb0e6f46
Code: f7 d8 64 89 04 25 d4 02 00 00 64 4c 8b 14 25 10 00 00 00 31 d2 49 81 c2 d0 02 00 00 31 f6 bf 11 00 20 01 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 31 01 00 00 85 c0 41 89 c4 0f 85 3b 01 00
RSP: 002b:00007ffd51b4a8e0 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffd51b4a8e0 RCX: 00007f8acb0e6f46
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffd51b4a940 R08: 0000000000006d23 R09: 0000000000006d23
R10: 00007f8acba03a70 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd51b4a900 R14: 0000000000000005 R15: 0000000000000005
Kernel Offset: disabled
Rebooting in 86400 seconds..