==================================================================
BUG: KCSAN: data-race in do_sendfile / ksys_write

write to 0xffff88810ad21468 of 8 bytes by task 2766 on cpu 1:
 ksys_write+0x101/0x180 fs/read_write.c:660
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810ad21468 of 8 bytes by task 2774 on cpu 0:
 do_sendfile+0x328/0xca0 fs/read_write.c:1230
 __do_sys_sendfile64 fs/read_write.c:1312 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2774 Comm: syz-executor.4 Not tainted 5.11.0-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: 2774 Comm: syz-executor.4 Not tainted 5.11.0-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:79 [inline]
 dump_stack+0x116/0x15d lib/dump_stack.c:120
 panic+0x1e7/0x5fa kernel/panic.c:231
 kcsan_report+0x67b/0x680 kernel/kcsan/report.c:634
 kcsan_setup_watchpoint+0x47b/0x4e0 kernel/kcsan/core.c:568
 do_sendfile+0x328/0xca0 fs/read_write.c:1230
 __do_sys_sendfile64 fs/read_write.c:1312 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e219
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f380cbd6c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045e219
RDX: 00000000200000c0 RSI: 0000000000000005 RDI: 0000000000000005
RBP: 000000000119c070 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000feff R11: 0000000000000246 R12: 000000000119c034
R13: 00007ffde25107ef R14: 00007f380cbd79c0 R15: 000000000119c034
Kernel Offset: disabled
Rebooting in 86400 seconds..